Master Sources Table
Each distinct Xray source identified on the sky is represented in the catalog by a single "master source" entry and one or more "perstack detection" entries, one for each stack in which the source has been detected and by one or more "perobservation detection" entries, one for each observation contribution to the stack in which the source has been detected. Many of the master source properties are populated from the properties of the Best Block (the one with the largest total exposure) from the Bayesian Block Analysis (e.g., aperture photometry).
Note: Source properties in the catalog which have a value for each science energy band (type "double[6]" and "integer[6]" in the table below) have the corresponding letters appended to their names. For example, "flux_aper_b" and "flux_aper_h" represent the backgroundsubtracted, aperturecorrected broadband and hardband energy fluxes, respectively.
Note: "Description" entries with a vertical bar running to the left of the text have more information available that will be displayed when the cursor hovers over the column description.
Column Name  Type  Units  Description  

acis_hetg_num  integer  total number of ACIS/HETG observations contributing to the Master Sources Table record of the source  
acis_hetg_time  double  total livetime for all ACIS/HETG observations contributing to the Master Sources Table record of the source  
acis_letg_num  integer  total number of ACIS/LETG observations contributing to the Master Sources Table record of the source  
acis_letg_time  double  total livetime for all ACIS/LETG observations contributing to the Master Sources Table record of the source  
acis_num  integer  total number of ACIS imaging observations contributing to the Master Sources Table record of the source  
acis_time  double  total livetime for all ACIS imaging observations contributing to the Master Sources Table record of the source  
apec_abund  double  abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_abund_hilim  double  abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)  
apec_abund_lolim  double  abundance of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
apec_abund_rhat  double  abundance convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_kt  double  keV  temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_kt_hilim  double  keV  temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)  
apec_kt_lolim  double  keV  temperature (kT) of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
apec_kt_rhat  double  temperature (kT) convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_nh  double  N _{HI atoms} 10^{20} cm^{2}  N_{H} column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_nh_hilim  double  N _{HI atoms} 10^{20} cm^{2}  N_{H} column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)  
apec_nh_lolim  double  N _{HI atoms} 10^{20} cm^{2}  N_{H} column density of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
apec_nh_rhat  double  N_{H} column density convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_norm  double  amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_norm_hilim  double  amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upperer confidence limit)  
apec_norm_lolim  double  amplitude of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
apec_norm_rhat  double  amplitude convergence criterion of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_stat  double  χ^{2} statistic per degree of freedom of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_z  double  redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
apec_z_hilim  double  redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)  
apec_z_lolim  double  redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
apec_z_rhat  double  redshift convergence criterion Redshift of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
bb_ampl  double 
amplitude of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model amplitude and the associated twosided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as: \[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{2} keV^{3} s^{1}}\right] \] 

bb_ampl_hilim  double 
amplitude of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
upperer confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model amplitude and the associated twosided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as: \[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{2} keV^{3} s^{1}}\right] \] 

bb_ampl_lolim  double 
amplitude of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model amplitude and the associated twosided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as: \[ A = \frac{2\pi}{c^{2} h^{3}} \left(\frac{R}{d}\right)^{2} = 9.884 \times 10^{31} \left(\frac{R}{d}\right)^{2} \left[\mathrm{cm^{2} keV^{3} s^{1}}\right] \] 

bb_ampl_rhat  double  amplitude convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum  
bb_kt  double  keV 
temperature (kT) of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

bb_kt_hilim  double  keV 
temperature (kT) of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

bb_kt_lolim  double  keV 
temperature (kT) of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit blackbody model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

bb_kt_rhat  double  temperature (kT) convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum  
bb_nh  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed blackbody model fit, in units of 10^{20} cm^{2}. 

bb_nh_hilim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed blackbody model fit, in units of 10^{20} cm^{2}. 

bb_nh_lolim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed blackbody model fit, in units of 10^{20} cm^{2}. 

bb_nh_rhat  double  N_{H} column density convergence criterion of the best fitting absorbed black body model spectrum to the source region aperture PI spectrum  
bb_stat  double 
χ^{2} statistic per degree of freedom of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the bestfitting blackbody model. 

brems_kt  double  keV 
temperature (kT) of the best fitting absorbed bremsstrahlung
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

brems_kt_hilim  double  keV 
temperature (kT) of the best fitting absorbed bremsstrahlung
model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

brems_kt_lolim  double  keV 
temperature (kT) of the best fitting absorbed bremsstrahlung
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model temperature (kT) in units of keV and the associated twosided 68% confidence limits. 

brems_kt_rhat  double  temperature (kT) convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum  
brems_nh  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
bremsstrahlung model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10^{20} cm^{2}. 

brems_nh_hilim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
bremsstrahlung model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10^{20} cm^{2}. 

brems_nh_lolim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
bremsstrahlung model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10^{20} cm^{2}. 

brems_nh_rhat  double  N_{H} column density convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum  
brems_norm  double 
amplitude of the best fitting absorbed bremsstrahlung model
spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model normalization and the associated twosided 68% confidence limits. The model normalization is defined by: \[ A = \frac{3.02 \times 10^{15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^{3} and \(D\) is the distance to the source in cm. 

brems_norm_hilim  double 
amplitude of the best fitting absorbed bremsstrahlung model
spectrum to the source region
aperture PI spectrum (68%
upperer confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model normalization and the associated twosided 68% confidence limits. The model normalization is defined by: \[ A = \frac{3.02 \times 10^{15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^{3} and \(D\) is the distance to the source in cm. 

brems_norm_lolim  double 
amplitude of the best fitting absorbed bremsstrahlung model
spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bestfit bremsstrahlung model normalization and the associated twosided 68% confidence limits. The model normalization is defined by: \[ A = \frac{3.02 \times 10^{15}}{4\pi D^{2}} \int n_{e} n_{i} dV \]where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^{3} and \(D\) is the distance to the source in cm. 

brems_norm_rhat  double  amplitude convergence criterion of the best fitting absorbed bremsstrahlung model spectrum to the source region aperture PI spectrum  
brems_stat  double 
χ^{2} statistic per degree of freedom of the best fitting
absorbed bremsstrahlung model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the bestfitting bremsstrahlung model. 

conf_flag  Boolean 
source may be confused (source and/or background regions
overlap in one or more contributing stacked observations)
From the Source Flags column descriptions page: The confusion flag for a compact source is a Boolean that has a value of TRUE if the confusion code for any contributing stacked observation detection indicates that the detection's source region ellipse is confused (i.e. overlaps one of more detection source region ellipses in another stacked observation). Otherwise, the value is FALSE. The confusion flag for an extended (convex hull) source is always NULL. 

dec  double  deg 
source position,
ICRS declination
From the Position and Position Errors column descriptions page: The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'. 

dither_warning_flag  Boolean 
highest statistically significant peak in the power spectrum
of the source region count rate occurs at
the dither frequency or
at a beat frequency of
the dither frequency in
one or more observations
From the Source Flags column descriptions page: The dither warning flag for a compact source is a Boolean that has a value of TRUE if the dither warning flag for any contributing stacked observation detection is TRUE. Otherwise, the value is FALSE. The dither warning flag for an extended (convex hull) source is always NULL. 

err_ellipse_ang  double  deg 
position angle
(referenced from local true north) of the major axis of
the 95% confidence
level error ellipse
From the Position and Position Errors column descriptions page: The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semimajor and semiminor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semimajor and semiminor axes correspond to the 95% confidence intervals along these axes. 

err_ellipse_r0  double  arcseconds 
major radius of the 95% confidence level position error
ellipse
From the Position and Position Errors column descriptions page: The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semimajor and semiminor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semimajor and semiminor axes correspond to the 95% confidence intervals along these axes. 

err_ellipse_r1  double  arcseconds 
minor radius of the 95%
confidence level position error ellipse
From the Position and Position Errors column descriptions page: The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semimajor and semiminor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semimajor and semiminor axes correspond to the 95% confidence intervals along these axes. 

extent_flag  Boolean 
source is extended, or deconvolved
source extent is inconsistent with a point
source at the 90% confidence level in one or more
observations and science energy bands
From the Source Flags column descriptions page: The extent flag for a compact source is a Boolean that has a value of TRUE if the deconvolved source extent is inconsistent with a point source at the 90% confidence level in any science energy band in any contributing observation. Otherwise, the value is FALSE. The extent flag for an extended (convex hull) source is always TRUE. 

flux_apec  double  ergs s^{1} cm^{2}  net integrated 0.57.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum  
flux_apec_aper  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_aper90  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_aper90_hilim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] (68% upper confidence limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_aper90_lolim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] (68% lower confidence limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_aper_hilim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] (68% upper confidence limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_aper_lolim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed APEC model [N_{H} = N_{H}(Gal); kT
= 6.5 keV] (68% lower confidence limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_apec_hilim  double  ergs s^{1} cm^{2}  net integrated 0.57.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% upper confidence limit)  
flux_apec_lolim  double  ergs s^{1} cm^{2}  net integrated 0.57.0 keV energy flux of the best fitting absorbed APEC model spectrum to the source region aperture PI spectrum (68% lower confidence limit)  
flux_aper  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90_avg  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90_avg_hilim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events (68% upper
confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90_avg_lolim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events (68% lower
confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90_hilim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events (68% upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper90_lolim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events (68% lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper_avg  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events for
each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper_avg_hilim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events (68%
upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper_avg_lolim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events (68%
lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper_hilim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events (68% upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_aper_lolim  double[6]  ergs s^{1} cm^{2} 
aperturecorrected net energy flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events (68% lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

flux_bb  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The blackbody flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed blackbody model, in units of erg/s/cm^{2}. 

flux_bb_aper  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_aper90  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_aper90_hilim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_aper90_lolim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_aper_hilim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_aper_lolim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed black body model [N_{H} =
N_{H}(Gal); kT = 0.75 keV] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_bb_hilim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The blackbody flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed blackbody model, in units of erg/s/cm^{2}. 

flux_bb_lolim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed black body
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed blackbody model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude. The blackbody flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed blackbody model, in units of erg/s/cm^{2}. 

flux_brems  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed bremsstrahlung model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bremsstrahlung flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed bremsstrahlung model, in units of erg/s/cm^{2}. 

flux_brems_aper  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_aper90  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_aper90_hilim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_aper90_lolim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_aper_hilim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_aper_lolim  double[6]  ergs s^{1} cm^{2} 
source region aperture
model energy flux inferred from the
canonical absorbed bremsstrahlung model [N_{H} =
N_{H}(Gal); kT = 3.5 keV] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_brems_hilim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed bremsstrahlung model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bremsstrahlung flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed bremsstrahlung model, in units of erg/s/cm^{2}. 

flux_brems_lolim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed bremsstrahlung model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed bremsstrahlung model is fit over the energy range 0.57.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude. The bremsstrahlung flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfit absorbed bremsstrahlung model, in units of erg/s/cm^{2}. 

flux_powlaw  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed powerlaw
model spectrum to the source region aperture
PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The power law model flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfitting absorbed power law model, in units of erg/s/cm^{2}. 

flux_powlaw_aper  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_aper90  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_aper90_hilim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_aper90_lolim  double[6]  ergs s^{1} cm^{2} 
PSF 90% ECF aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_aper_hilim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] (68% upper confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_aper_lolim  double[6]  ergs s^{1} cm^{2} 
source region aperture model
energy flux inferred from the canonical
absorbed power law model [N_{H} =
N_{H}(Gal); γ = 2.0] (68% lower confidence
limit) for each science energy band
From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page: The aperture model energy fluxes and associated twosided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure. 

flux_powlaw_hilim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed powerlaw
model spectrum to the source region aperture
PI spectrum (68% upper
confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The power law model flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfitting absorbed power law model, in units of erg/s/cm^{2}. 

flux_powlaw_lolim  double  ergs s^{1} cm^{2} 
net integrated 0.57.0 keV energy flux of the best fitting
absorbed powerlaw
model spectrum to the source region aperture
PI spectrum (68% lower
confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The power law model flux and the associated twosided 68% confidence limits represent the integrated 0.57 keV flux derived from the bestfitting absorbed power law model, in units of erg/s/cm^{2}. 

gal_b  double  deg  source position, Galactic latitude (equinox J2000.0, epoch J2000.0)  
gal_l  double  deg  source position, galactic longitude (equinox J2000.0, epoch J2000.0)  
hard_hm  double 
ACIS hard (2.07.0 keV)  medium (1.22.0 keV) energy
band hardness
ratio
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_hm_hilim  double 
ACIS hard (2.07.0 keV)  medium (1.22.0 keV) energy
band hardness
ratio (68% upper confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_hm_lolim  double 
ACIS hard (2.07.0 keV)  medium (1.22.0 keV) energy
band hardness
ratio (68% lower confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_hs  double 
ACIS hard (2.07.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_hs_hilim  double 
ACIS hard (2.07.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio (68% upper confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_hs_lolim  double 
ACIS hard (2.07.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio (68% lower confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_ms  double 
ACIS medium (1.22.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_ms_hilim  double 
ACIS medium (1.22.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio (68% upper confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hard_ms_lolim  double 
ACIS medium (1.22.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio (68% lower confidence limit)
From the Spectral Properties column descriptions page: Hardness ratios appear in both the Master Sources Table and the PerObservation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the PerObservation Detections Table. Only energy bands hard (h, 2.07.0 keV), medium (m, 1.22.0 keV) and soft (s, 0.51.2 keV) are used. For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF: \[ P_{H_{xy}}\left( H_{xy} \right) dH_{xy} = \int_{F_{xy}=0}^{\infty} P_{x}\left( \frac{\left( 1 + H_{xy} \right) F_{xy}}{2} \right) P_{y}\left( \frac{\left( 1  H_{xy} \right) F_{xy}}{2} \right) \frac{F_{xy}}{2} \ dH_{xy} dF_{xy} \]By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the mediumtosoft band hardness ratio, defined as: \[ \mathit{hard\_ms} = \frac{F(m)  F(s)}{F(m) + F(s)} \]Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard. As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog. Hardness ratios using the broad, ultrasoft, and HRC bands are not included in the catalog. The twosided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range 1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block. In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo. 

hrc_hetg_num  integer  total number of HRC/HETG observations contributing to the Master Sources Table record of the source  
hrc_hetg_time  double  total livetime for all HRC/HETG observations contributing to the Master Sources Table record of the source  
hrc_letg_num  integer  total number of HRC/LETG observations contributing to the Master Sources Table record of the source  
hrc_letg_time  double  total livetime for all HRC/LETG observations contributing to the Master Sources Table record of the source  
hrc_num  integer  total number of HRC imaging observations contributing to the Master Sources Table record of the source  
hrc_time  double  total livetime for all HRC imaging observations contributing to the Master Sources Table record of the source  
kp_intra_prob  double[6] 
intraobservation Kuiper's test variability probability
(highest value across all observations); ACIS for each
science energy band
From the Source Variability column descriptions page: The GregoryLoredo, KolmogorovSmirnov (KS) test, and Kuiper's test intraobservation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry). 

ks_intra_prob  double[6] 
intraobservation KolmogorovSmirnov test variability
probability (highest value across all observations)
for each science energy band
From the Source Variability column descriptions page: The GregoryLoredo, KolmogorovSmirnov (KS) test, and Kuiper's test intraobservation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry). 

likelihood  double 
highest detection loglikelihood across all stacked
observations and science energy bands
From the Source Significance column descriptions page: The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood. The fundamental metric used to decide whether a source is included in CSC 2.1 is the likelihood, \[ \mathcal{L}=\ln{P} \ \mathrm{,} \]where \(P\) is the probability that an MLE fit to a point or extended source model, in a region with no source, would yield a change in fit statistic as large or larger than that observed, when compared to a fit to background only. The likelihood is closely related to the probability, \(P_{\mathrm{Pois}}\), that a Poisson distribution with a mean background in the source aperture would produce at least the number of counts observed in the aperture. This quantity, called detect_significance, is also reported in CSC 2.1. Smoothed background maps are used to estimate mean background, and detect_significance is expressed in terms of the number of \(\sigma\), \(z\), in a zeromean, unit standard deviation Gaussian distribution that would yield an upper integral probability \(P_{\mathrm{Gaus}}\), from \(z\) to \(\infty\), equivalent to \(P_{\mathrm{Pois}}\). That is, \[ P_{\mathrm{Pois}} = P_{\mathrm{Gaus}} \]where \[ P_{\mathrm{Gaus}} = \int_{z}^{\infty} \frac{e^{x^{2}/2}}{\sqrt{2\pi}} dx \] 

likelihood_class  string  highest detection likelihood classification across all stacked observations and science energy bands  
major_axis  double[6]  arcseconds  1σ radius along the major axis of the ellipse defining the deconvolved source extent for each science energy band  
major_axis_hilim  double[6]  arcseconds  1σ radius along the major axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band  
major_axis_lolim  double[6]  arcseconds  1σ radius along the major axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band  
man_add_flag  Boolean 
source was manually added in the catalog via human review
From the Source Flags column descriptions page: The manual source addition flag for a compact source is a Boolean that has a value of TRUE if all of the stacked observation detections that contribute to the master source were manually added to the catalog by human review, i.e., man_add_flag is TRUE for all such detections. Otherwise, the value is FALSE. The manual source addition flag for an extended (convex hull) source is set to TRUE if any of the stacked observation detections that contribute to the master source were manually added to the catalog by human review. Otherwise, the value is FALSE. 

man_inc_flag  Boolean 
source was manually included in the catalog via human review
(detection was rejected by automated criteria)
From the Source Flags column descriptions page: The manual source inclusion flag for a compact source is a Boolean that has a value of TRUE if all of the stacked observation detections that contribute to the master source were manually included in the catalog by human review, i.e., man_inc_flag is TRUE for all such detections. Otherwise, the value is FALSE. 

man_match_flag  Boolean 
source detections were manually matched between overlapping
stacked observations via human review
From the Source Flags column descriptions page: The manual match flag for a compact of extended (convex hull) source is a Boolean that has a value of TRUE if the set of stacked observation detections contributing to the master source was manually modified by human review, i.e. the observation detections were not matched, or were matched incorrectly, by the detection matching algorithm. Otherwise, the value is FALSE. 

man_pos_flag  Boolean 
best fit source position was manually modified via human
review
From the Source Flags column descriptions page: The manual source position flag for a compact source is a Boolean that has a value of TRUE if the final source position was manually modified by human review in all of the stacked observation detections that contribute to the master source, i.e., man_pos_flag is TRUE for all such detections. Otherwise, the value is FALSE. The manual source position flag for an extended (convex hull) source is set to TRUE if the final source position was manually modified by human review in any of the stacked observation detections that contribute to the master source, or if the final master source position was manually modified from the fluxweighted centroid position by human review. 

man_reg_flag  Boolean 
source region parameters (dimensions, initial guess position
input to the Maximum Likelihood
Estimator fit) were manually modified via human
review
From the Source Flags column descriptions page: The manual source region parameters flag for a compact source is a Boolean that has a value of TRUE if the source region parameters were manually modified by human review in all of the stacked observation detections that contribute to the master source, i.e., man_reg_flag is TRUE for all of the contributing stacked observation detections. Otherwise, the value is FALSE. The manual source inclusion flag for an extended (convex hull) source is set to TRUE if the source region parameters were manually modified by human review in any of the stacked observation detections that contribute to the master source, or if the source region parameters for the master extended (convex hull) source was manually modified by human review. Otherwise, the value is FALSE. 

minor_axis  double[6]  arcseconds  1σ radius along the minor axis of the ellipse defining the deconvolved source extent for each science energy band  
minor_axis_hilim  double[6]  arcseconds  1σ radius along the minor axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band  
minor_axis_lolim  double[6]  arcseconds  1σ radius along the minor axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band  
name  string  source name in the form "2CXO Jhhmmss.s{+}ddmmss"  
nh_gal  double  N _{HI atoms} 10^{20} cm^{2}  Galactic N_{H} column density in direction of source  
phot_nsrcs  long  number of sources simultaneously fit to compute aperture photometry quantitites  
photflux_aper  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90_avg  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90_avg_hilim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events (68% upper
confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90_avg_lolim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, averaged over all contributing observations,
and calculated by counting Xray events (68% lower
confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90_hilim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events (68% upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper90_lolim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the PSF 90%
ECF aperture, best estimate derived from the longest block
of a multiband, fluxordered Bayesian Block analysis of the
contributing observations, and calculated by counting Xray
events (68% lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper_avg  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events for
each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper_avg_hilim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events (68%
upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper_avg_lolim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, averaged over all contributing
observations, and calculated by counting Xray events (68%
lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the mean backgroundsubtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper_hilim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events (68% upper confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

photflux_aper_lolim  double[6]  photons s^{1} cm^{2} 
aperturecorrected net photon flux inferred from the source
region aperture, best estimate derived from the longest
block of a multiband, fluxordered Bayesian Block analysis
of the contributing observations, and calculated by counting
Xray events (68% lower confidence limit) for each science energy band
From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page: Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine backgroundmarginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits. Fluxes are determined for each perobservation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits. The aperture source photon and energy fluxes and associated twosided confidence limits represent the 'best estimate' backgroundsubtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^{1} cm^{2} to ergs s^{1} cm^{2} is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. 

pileup_flag  Boolean 
ACIS pileup fraction exceeds ~10% in all observations;
source properties may be affected
From the Source Flags column descriptions page: The pileup warning flag for a compact source is a Boolean that has a value of TRUE if the pileup fraction exceeds ~10% for all contributing ACIS stacked observation detections and energy bands, i.e., pileup_flag is TRUE for all such detections. Otherwise, the value is FALSE. The pileup warning flag for an extended (convex hull) source is always NULL. 

pos_angle  double[6]  deg  position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent for each science energy band  
pos_angle_hilim  double[6]  deg  position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent (68% upper confidence limit) for each science energy band  
pos_angle_lolim  double[6]  deg  position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved source extent (68% lower confidence limit) for each science energy band  
powlaw_ampl  double 
amplitude of the best fitting
absorbed powerlaw
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit amplitude of the power law model and associated twosided 68% confidence limits in units of photons/s/cm^{2}/keV defined at 1 keV. 

powlaw_ampl_hilim  double 
amplitude of the best fitting
absorbed powerlaw
model spectrum to the source region
aperture PI spectrum (68%
upper confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit amplitude of the power law model and associated twosided 68% confidence limits in units of photons/s/cm^{2}/keV defined at 1 keV. 

powlaw_ampl_lolim  double 
amplitude of the best fitting
absorbed powerlaw
model spectrum to the source region
aperture PI spectrum (68%
lower confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit amplitude of the power law model and associated twosided 68% confidence limits in units of photons/s/cm^{2}/keV defined at 1 keV. 

powlaw_ampl_rhat  double  amplitude convergence criterion of the best fitting absorbed powerlaw model spectrum to the source region aperture PI spectrum  
powlaw_gamma  double 
photon index, defined as F_{E} ∝
E^{γ}, of the best fitting absorbed
powerlaw model
spectrum to the source region aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit power law photon index and the associated twosided 68% confidence limits, \(\gamma\), defined as: \[ F_{E} \propto E^{\gamma} \] 

powlaw_gamma_hilim  double 
photon index, defined as F_{E} ∝
E^{γ}, of the best fitting absorbed
powerlaw model
spectrum to the source region aperture PI spectrum (68% upper confidence
limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit power law photon index and the associated twosided 68% confidence limits, \(\gamma\), defined as: \[ F_{E} \propto E^{\gamma} \] 

powlaw_gamma_lolim  double 
photon index, defined as F_{E} ∝
E^{γ}, of the best fitting absorbed
powerlaw model
spectrum to the source region aperture
PI spectrum (68% lower
confidence limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit power law photon index and the associated twosided 68% confidence limits, \(\gamma\), defined as: \[ F_{E} \propto E^{\gamma} \] 

powlaw_gamma_rhat  double  photon index convergence criterion of the best fitting absorbed powerlaw model spectrum to the source region aperture PI spectrum  
powlaw_nh  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
powerlaw
model spectrum to the source region aperture
PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed power law model spectral fit in units of 10^{20} cm^{2}. 

powlaw_nh_hilim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
powerlaw model
spectrum to the source region aperture PI spectrum (68% upper confidence
limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed power law model spectral fit in units of 10^{20} cm^{2}. 

powlaw_nh_lolim  double  N _{HI atoms} 10^{20} cm^{2} 
N_{H} column density of the best fitting absorbed
powerlaw model
spectrum to the source region aperture PI spectrum (68% lower confidence
limit)
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The bestfit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated twosided 68% confidence limits from an absorbed power law model spectral fit in units of 10^{20} cm^{2}. 

powlaw_nh_rhat  double  N_{H} column density convergence criterion of the best fitting absorbed powerlaw model spectrum to the source region aperture PI spectrum  
powlaw_stat  double 
χ^{2} statistic per degree of freedom of the best fitting
absorbed powerlaw
model spectrum to the source region
aperture PI spectrum
From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page: The master source spectral fit will use the ACIS observations contained in the best block provided the total summed backgroundsubtracted counts for all of the observations is at least 150 counts in the 0.57.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux. The absorbed power law model spectral fit is performed over the energy range 0.57.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude. The power law model spectral fit statistic is defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the bestfitting absorbed power law model. 

ra  double  deg 
source position,
ICRS right ascension
From the Position and Position Errors column descriptions page: The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'. 

sat_src_flag  Boolean 
source is saturated in all observations; source properties
are unreliable
From the Source Flags column descriptions page: The saturated source flag is for a compact source is a Boolean that has a value of TRUE if all contributing observations are ACIS observations and all stacked observation detections are significantly piledup, i.e., sat_src_flag is TRUE for all of the contributing stacked observation detections. Source properties (including the pileup warning flag) are unreliable for all ACIS energy bands. Otherwise, the value is FALSE. sat_src_flag for an extended (convex hull) source is always NULL. 

significance  double 
highest flux
significance across all stacked
observations and science energy bands
From the Source Significance column descriptions page: The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood. Flux significance is a simple estimate of the ratio of the flux measurement to its average error. The mode of the marginalized probability distribution for photflux_aper is used as the flux measurement and the average error, \(\sigma_{e}\), is defined to be: \[ \sigma_{e} = \frac{\mathit{photflux\_aper\_hilim}  \mathit{photflux\_aper\_lolim}}{2} \]which are both used to estimate flux significance. 

src_area  double[6]  sq. arcseconds  area of the deconvolved source extent ellipse, or area of the source polygon for extended sources for each science energy band  
streak_src_flag  Boolean 
source is located on an ACIS readout
streak in all observations; source properties
may be affected
From the Source Flags column descriptions page: The streak source flag for a compact detection is a Boolean that has a value of TRUE if all of the contributing observations are ACIS observations and all stacked observation detection source regions overlap a defined region enclosing an identified readout streak, i.e. streak_src_flag is TRUE for all of the contributing stacked observation detections. Otherwise, the value is FALSE. The streak source flag for an extended (convex hull) is TRUE if any contributing observations are ACIS observations and any stacked observation detection source region overlaps a defined region enclosing an identified readout streak. Otherwise, the value is FALSE. 

var_flag  Boolean 
source displays flux variability within one or more
observations, or between observations, in one or more energy
bands
From the Source Flags column descriptions page: The variability flag for a compact source is a Boolean that has a value of TRUE if variability is detected (the corresponding var_index value is ≥6) within any single observation or between any pair of observations contributing to the master source, in any science energy band. Otherwise, the value is FALSE. The variability flag for an extended (convex hull) source is always NULL. 

var_inter_hard_flag  Boolean 
source hardness
ratios are statistically inconsistent between
two or more observations
From the Source Flags column descriptions page: The interobservation variable hardness ratio flag for a compact source is a Boolean that has a value of TRUE if one or more of the hardness ratios computed for any of the contributing observation detections is statistically inconsistent with the corresponding hardness ratios computed for any other contributing observation detections. Otherwise, the value is FALSE. The interobservation variable hardness ratio flag for an extended (convex hull) source is always NULL. From the Source Variability column descriptions page: A Boolean set to FALSE if var_inter_hard_prob is below 0.3 for all three hardness ratios, and set to TRUE otherwise. 

var_inter_hard_prob_hm  double 
interobservation ACIS hard (2.07.0 keV)  medium (1.22.0 keV) energy
band hardness
ratio variability probability
From the Source Variability column descriptions page: The interobservation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the interobservation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands. 

var_inter_hard_prob_hs  double 
interobservation ACIS hard (2.07.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio variability probability
From the Source Variability column descriptions page: The interobservation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the interobservation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands. 

var_inter_hard_prob_ms  double 
interobservation ACIS medium (1.22.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio variability probability
From the Source Variability column descriptions page: The interobservation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the interobservation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands. 

var_inter_hard_sigma_hm  double 
interobservation ACIS hard (2.07.0 keV)  medium (1.22.0 keV) energy
band hardness
ratio variability standard deviation
From the Source Variability column descriptions page: Similarly to var_inter_sigma, the interobservation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference: \[ \left hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}}  hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right \]Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios. 

var_inter_hard_sigma_hs  double 
interobservation ACIS hard (2.07.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio variability standard deviation
From the Source Variability column descriptions page: Similarly to var_inter_sigma, the interobservation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference: \[ \left hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}}  hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right \]Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios. 

var_inter_hard_sigma_ms  double 
interobservation ACIS medium (1.22.0 keV)  soft (0.51.2 keV) energy
band hardness
ratio variability standard deviation
From the Source Variability column descriptions page: Similarly to var_inter_sigma, the interobservation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference: \[ \left hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{max}}  hard_{\left\langle band_{1}band_{2}\right\rangle}^{\mathrm{i,max}} \right \]Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios. 

var_inter_index  integer[6] 
interobservation variability index in the range [0,
10]: indicates whether the source region photon flux is
constant between observations for each science energy band
From the Source Variability column descriptions page: The interobservation variability index (var_inter_index) is an integer value in the range \([0,8]\) that is derived according to the estimated value of the quantity \(D/(N1)\) defined above. It is used to evaluate whether the source region photon flux is constant between the observations. The degree of confidence in variability expressed by this index is similar to that of the intraobservation variability index. Below we tabulate the association between the value of \(D/(N1)\) and interobservation variability index.


var_inter_prob  double[6] 
interobservation variability probability, calculated
from the chi^2 distribution of the photon fluxes of the
individual observations for each science energy band
From the Source Variability column descriptions page: The interobservation variability probability (var_inter_prob) is a value that records the probability that the source region photon flux varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. Given the \(N\) individual Bayesian probability distribution of the aperture fluxes for the same source in \(N\) different observations (their means and standard deviations), we estimate for each band the maximum likelihood \(\mathcal{L}_{1}^{\mathrm{max}}\) and the corresponding maximizing arguments \(F_{\left\langle band \right\rangle}^{i,\mathrm{max}}\), of the observed fluxes assuming a different flux for each observation, as well as the maximum likelihood \(\mathcal{L}_{2}^{\mathrm{max}}\) and the corresponding maximizing argument \(F_{\left\langle band \right\rangle}^{\mathrm{max}}\) of the observed fluxes assuming a single flux (the latter is the null hypothesis of no variability). As per Wilks' theorem, the quantity: \[ D \equiv 2 \left( \log{\mathcal{L}_{1}^{\mathrm{max}}}  \log{\mathcal{L}_{2}^{\mathrm{max}}} \right) \]follows \(\chi^{2}\) distribution with \(N1\) degrees of freedom, under the null hypothesis. Therefore, the null hypothesis (nonvariability) is rejected with a probability proportional to the cumulative distribution of the \(\chi^{2}\) statistic for values smaller than the estimated \(D\). The quantity var_inter_prob represents this cumulative probability, and therefore gives the probability that the source is variable. The reason for this careful definition is that the probabilities for intraobservation and interobservation variability are, by necessity, of a different nature. Whereas one can say with reasonable certainty whether a source was variable during an observation covering a contiguous time interval, when comparing measured fluxes from different observations one knows nothing about the source's behavior during the intervening interval(s). Consequently, when the interobservation variability probability is high (e.g., var_inter_prob > 0.7), one can confidently state that the source is variable on longer time scales, but when the probability is low, all one can say is that the observations are consistent with a constant flux. 

var_inter_sigma  double[6]  photons s^{1} cm^{2} 
interobservation flux variability standard deviation;
the spread of the individual observation photon fluxes about
the error weighted mean for each science energy band
From the Source Variability column descriptions page: The interobservation flux variability (var_inter_sigma) is the absolute value of the difference between the error weighted mean of the source region photon flux density PDF when a single flux is assumed \(\left( F_{\left\langle band \right\rangle}^{\mathrm{max}} \right)\), and the mean of the source region photon flux density PDF for the individual observation that maximizes the absolute value of the difference \(\left( F_{\left\langle band \right\rangle}^{i,\mathrm{max}} \right)\): \[ \left F_{\left\langle band \right\rangle}^{\mathrm{max}}  F_{\left\langle band \right\rangle}^{i,\mathrm{max}} \right \]Of all the contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation fluxes. 

var_intra_index  integer[6] 
intraobservation
GregoryLoredo variability index in the range [0,
10]: indicates whether the source region photon flux is
constant within an observation (highest value across all
observations) for each science energy band
From the Source Variability column descriptions page: The intraobservation variability index (var_intra_index) represents the highest value of the variability indices (var_index) calculated for each of the contributing observations. 

var_intra_prob  double[6] 
intraobservation
GregoryLoredo variability probability (highest
value across all observations) for each science energy band
From the Source Variability column descriptions page: The GregoryLoredo, KolmogorovSmirnov (KS) test, and Kuiper's test intraobservation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry). 