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Last modified: 25 April 2018

URL: http://cxc.harvard.edu/csc/columns/flags.html

Source Flags


The source flags highlight significant issues identified during processing that could affect cataloged source properties.


Confusion Flag

Master Sources Table:
conf_flag

The confusion flag is a Boolean that has a value of FALSE if the confusion codes for all contributing observations do not indicate that the source detection region is confused (i.e. not found to contain multiple sources, does not overlap other source detection regions, and contains no overlapping source region ellipses in all contributing observations). Otherwise, the value is TRUE.

Stacked Observation Detections Table:
conf_code
Per-Observation Detections Table:
conf_code

The confusion code is an 16-bit coded bytes that has all bits set to zero if the source region has only one source component associated with it in all source detection energy bands, and the source and background regions do not overlap another source or background region in any source detection energy band. Otherwise, the bits are set as follows:

Bit Value Code
1 1 Background region overlaps another background region
2 2 Background region overlaps another source region
3 4 Source detection region overlaps another background region
4 8 Source detection region overlaps another source region
5 16
6 32
7 64
8 128
9 256 Compact detection is overlaid on an extended detection
10 512
11 1024
12 2048
13 4096
14 8192
15 16384
16 32768

Dither Warning

Master Sources Table:
dither_warning_flag
Stacked Observation Detections Table:
dither_warning_flag
Per-Observation Detections Table:
dither_warning_flag

The dither warning flag is a boolean that has TRUE if the highest statistically significant peak in the power spectrum of the source detection region count rate for each science energy band occurs either at the dither frequency of the observation or at a beat frequency of the dither frequency. Otherwise, the value is FALSE.


Chip Edge Code

Stacked Observation Detections Table:
edge_code
Per-Observation Detections Table:
edge_code

The chip edge code is an 16-bit coded bytes that has all bits set to zero if the source position, source region, and background region do not dither off a chip boundary (the edge of the unmasked area of the active region of the ACIS CCD or HRC microchannel plate segment, as appropriate) during the observation. Otherwise, the bits are set as follows:

Bit Value Code
1 1 Background region dithers off detector boundary
2 2 Source region dithers off detector boundary
3 4 Detection position dithers off detector boundary
4 8
5 16
6 32
7 64
8 128
9 256
10 512
11 1024
12 2048
13 4096
14 8192
15 16384
16 32768

Extent Flag

Master Sources Table:
extent_flag

The extent flag 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 with a flux significance >= 3.0 in any contributing observation. Otherwise, the value is FALSE.

Stacked Observation Detections Table:
extent_code
Per-Observation Detections Table:
extent_code

The extent code is an 16-bit coded bytes that has all bits set to zero if a wavelet transform analysis of counts in the source region is consistent with a point source at the 90% confidence level in all science energy bands. Otherwise, the bits are set as follows:

Bit Value Code Expanded Code (mrgsrc)
1 1 Deconvolved source extent is not consistent with point source at the 90% confidence level in the ultrasoft band possibly extended ACIS ultrasoft band
2 2 Deconvolved source extent is not consistent with point source at the 90% confidence level in the soft band possibly extended ACIS soft band
3 4 Deconvolved source extent is not consistent with point source at the 90% confidence level in the medium band possibly extended ACIS medium band
4 8 Deconvolved source extent is not consistent with point source at the 90% confidence level in the hard band possibly extended ACIS hard band
5 16 Deconvolved source extent is not consistent with point source at the 90% confidence level in the broad band possibly extended ACIS broad band
6 32 Deconvolved source extent is not consistent with point source at the 90% confidence level in the wide band possibly extended HRC wide band
7 64
8 128
9 256 Extended detection definitely extended ACIS ultrasoft band
10 512 definitely extended ACIS soft band
11 1024 definitely extended ACIS medium band
12 2048 definitely extended ACIS hard band
13 4096 definitely extended ACIS broad band
14 8192
15 16384 definitely extended HRC wide band
16 32768

Manual Match Flag

The manual match flag appears only in the Master Sources Table (man_match_flag).

The manual match flag is a Boolean that has a value of TRUE if the set of individual source observations contributing to the Release 2 master source observation were manually selected and modified by human review, e.g. in the event that the source regions contained in the set of contributing individual source observations could not be automatically matched. Otherwise, the value is FALSE.


Manual Source Addition Flag

Master Sources Table:
man_add_flag
Stacked Observation Detections Table:
man_add_flag

The manual source addition flag is a Boolean that indicates if the detection was manually included in the catalog.


Manual Source Region Inclusion Flag

Master Sources Table:
man_inc_flag

The manual source region inclusion flag is a Boolean that has a value of TRUE if the source region was manually included in all of the contributing observations by human review (i.e. where automated source detection failed). Otherwise, the value is FALSE.

Stacked Observation Detections Table:
man_inc_flag

The manual source region inclusion flag is a Boolean that has a value of TRUE if the source region was included in this catalog after manual review. Otherwise, the value is FALSE.


Manual Source Region Parameters Flag

Master Sources Table:
man_reg_flag

The manual source region parameters flag is a Boolean that has a value of TRUE if the source region parameters were manually modified in all of the contributing observations by human review in the event of extreme pile-up. Otherwise, the value is FALSE.

Stacked Observation Detections Table:
man_reg_flag

The manual source region parameters flag is a Boolean that has a value of TRUE if the source region parameters were included in this catalog after manual review. Otherwise, the value is FALSE.


Manual Source Region Position Flag

Master Sources Table:
man_pos_flag
Stacked Observation Detections Table:
man_pos_flag

The manual source detection position flag is a Boolean that indicates if the source position was manually adjusted.


Multi-Chip Code

Stacked Observation Detections Table:
multi_chip_code
Per-Observation Detections Table:
multi_chip_code

The multi-chip code is an 16-bit coded bytes that has all bits set to zero if the source position, source region, and background region do not dither between two chips (ACIS CCDs or HRC plates) during the observation. Otherwise, the bits are set as follows:

Bit Value Code
1 1 Background region dithers across two chips
2 2 Background region dithers across more than two chips
3 4 Source region dithers across two chips
4 8 Source region dithers across more than two chips
5 16 Detection position dithers across two chips
6 32 Detection position dithers across more than two chips
7 64
8 128
9 256
10 512
11 1024
12 2048
13 4096
14 8192
15 16384
16 32768

Pileup Warning Flag

Master Sources Table:
pileup_warning
Stacked Observation Detections Table:
pileup_warning

The pileup warning flag is a Boolean that has a value of FALSE if the pileup fraction does not exceed ~10% for all contributing ACIS observations and source detection energy bands. Otherwise, the value is TRUE.

Per-Observation Detections Table:
pileup_warning

The pileup warning flag is a double precision value that reports the total number of counts in the broad science energy band per ACIS frame in the source region, normalized by the number of pixels in the source region, averaged over the observation. This value may be correlated with pileup models to crudely estimate the pileup fraction of the source.

The value is unreliable if the saturated source flag is TRUE.


Saturated Source Flag

Master Sources Table:
sat_src_flag

The saturated source flag is a Boolean that has a value of TRUE if all of the contributing observations are ACIS observations that are significantly piled-up, to the extent that the source image may be flat-topped or have a central hole. Otherwise, the value is FALSE.

Stacked Observation Detections Table:
sat_src_flag
Per-Observation Detections Table:
sat_src_flag

The saturated source flag is a Boolean that has a value of TRUE if the observation was obtained using ACIS and if the source is likely severely piled-up, to the extent that the source image may be flat-topped or have a central hole. Otherwise, the value is FALSE.

If the value is TRUE, the pileup warning flag value is unreliable.


Streak Source Flag

Master Sources Table:
streak_src_flag

The streak source flag is a Boolean that has a value of TRUE if all of the contributing observations are ACIS observations and contain source regions that overlap a defined region enclosing an identified readout streak. Otherwise, the value is FALSE.

Stacked Observation Detections Table:
streak_src_flag
Per-Observation Detections Table:
streak_src_flag

The streak source flag is a Boolean that has a value of TRUE if the observation was obtained using ACIS and if the mean chip coordinates of the source region fall within the readout streak region. Otherwise, the value is FALSE.


Variability Flag

Master Sources Table:
var_flag
Stacked Observation Detections Table:
var_flag

The variability flag is a Boolean that has a value of FALSE if variability is not detected within any single observation or between any pair of observations in any science energy band. Otherwise, the value is TRUE.

Per-Observation Detections Table:
var_code

The variability code is an 16-bit coded bytes that has all bits set to zero if variability is not detected within the observation in any science energy band. Otherwise, the bits are set as follows:

Bit Value Code
1 1 Intra-observation variability was detected in the ultrasoft (u) band
2 2 Intra-observation variability was detected in the soft (s) band
3 4 Intra-observation variability was detected in the medium (m) band
4 8 Intra-observation variability was detected in the hard (h) band
5 16 Intra-observation variability was detected in the broad (b) band
6 32 Intra-observation variability was detected in the wide (w) band
7 64
8 128
9 256
10 512
11 1024
12 2048
13 4096
14 8192
15 16384
16 32768

The appropriate bit in the variability code corresponding to a specific science energy band shall be set to 0 if the variability index for that science energy band is less than or equal to 2, otherwise the bit shall be set to 1.


Inter-observation Variable Hardness Ratio Flag

Master Sources Table:
var_inter_hard_flag
Stacked Observation Detections Table:
var_inter_hard_flag

The inter-observation variable hardness ratio flag consists of a Boolean whose value shall be TRUE if one or more of the hardness ratios computed for any of the individual source observations contributing to the Release 2 master source observation is statistically inconsistent with the corresponding hardness ratios computed for all of the other contributing individual source observations. Otherwise, the inter-observation variable hardness ratio flag shall be FALSE.


Last modified: 25 April 2018
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