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Last modified: 13 December 2012

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.

Source Observations Table:
conf_code

The confusion code is an 8-bit coded byte 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:

  • 1 = Multiple sources identified within the source detection region
  • 2 = Source detection region overlaps another source detection region
  • 4 = Source detection region overlaps another background region
  • 8 = Background region overlaps another source detection region
  • 16 = Background region overlaps another background region

Chip Edge Code

The chip edge code appears only in the Source Observations Table (edge_code).

The chip edge code is an 8-bit coded byte 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:

  • 1 = Source position dithers off any chip edge during the observation
  • 2 = Source region dithers off any chip edge during the observation
  • 4 = Background region dithers off any chip edge during the observation

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.

Source Observations Table:
extent_code

The extent code is an 8-bit coded byte 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:

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 current 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 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.

Source Observations 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.

Source Observations 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.

Multi-Chip Code

The multi-chip code appears only in the Source Observations Table (multi_chip_code).

The multi-chip code is an 8-bit coded byte 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:

  • 1 = Source position dithers across two chips during the observation
  • 2 = Source region dithers across two chips during the observation
  • 4 = Background region dithers across two chips during the observation
  • 8 = Source position dithers across more than two chips during the observation
  • 16 = Source region dithers across more than two chips during the observation
  • 32 = Background region dithers across more than two chips during the observation

Pileup Warning Flag

Master Sources 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.

Source Observations 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.

Source Observations 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.

Source Observations 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

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.

Source Observations:
var_code

The variability code is an 8-bit coded byte 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:

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

The inter-observation variable hardness ratio flag appears only in the Master Sources 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 current 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: 13 December 2012
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