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Last modified: 19 September 2019

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/Code

Master Sources Table:
conf_flag

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.

Stacked Observation Detections Table:
conf_code

The confusion code for a compact detection is a 16-bit coded integer that has all bits set to zero if the detection's source and backgroun region ellipses do not overlap another source or background region in any source detection energy band, and the compact detection does not overlay an extended detection. 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 region overlaps another background region
4 8 Source 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

The confusion code for an extend (convex hull) detection is always NULL.

Per-Observation Detections Table:
conf_code

The confusion code in the per-observation detections table is defined identically to the confusion code in the stacked observations detections table.


Dither Warning Flag

Master Sources Table:
dither_warning_flag

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.

Stacked Observation Detections Table:
dither_warning_flag

The dither warning flag for a compact detection is a Boolean that has a value of TRUE if the dither warning flag for any contributing per-observation detection is TRUE. Otherwise, the value is FALSE.

The dither warning flag for an extended (convex hull) source is always NULL.

Per-Observation Detections Table:
dither_warning_flag

The dither warning flag for a compact detection is a Boolean that has a value of TRUE if the highest statistically significant peak in the power spectrum of the detection's source region ellipse count rate at the dither frequency of at a beat frequency of the dither frequency of the observation in any science energy band. Otherwise, the value is False.

The dither warning flag for an extended (convex hull) source is always NULL.


Edge Code

Stacked Observation Detections Table:
edge_code

The edge code for a compact or extended (convex hull) detection is a 16-bit coded integer that has all bits set to zero if the detection's 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

Note that an extended (convex hull) detection (or associated background region) that extends across more than one chip by definition must dither off the chip boundary.

Per-Observation Detections Table:
edge_code

The edge code in the per-observation detections table is defined identically to the edge code in the stacked observations detections table.


Extent Flag

Master Sources Table:
extent_flag

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.

Stacked Observation Detections Table:
extent_code

The extent code for a compact detection is a 16-bit coded integer that has all bits set to zero if a wavelet transform analysis of counts in the detection's source region ellipse 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
1 1 Deconvolved compact detection extent is not consistent with point source at the 90% confidence level in the ACIS ultrasoft energy band
2 2 Deconvolved compact detection extent is not consistent with point source at the 90% confidence level in the ACIS soft energy band
3 4 Deconvolved compact detection extent is not consistent with point source at the 90% confidence level in the ACIS medium energy band
4 8 Deconvolved compact detection extent is not consistent with point source at the 90% confidence level in the ACIS hard energy band
5 16 Deconvolved compact detection extent is not consistent with point source at the 90% confidence level in the ACIS broad energy band
6 32 Deconvolved compact detection extend is not consistent with point source at the 90% confidence level in the HRC wide energy band
7 64
8 128
9 256 Extended detection
10 512
11 1024
12 2048
13 4096
14 8192
15 16384
16 32768

The extent code for an extended (convex hull) detection is always set to 256 (Extended detection).

Per-Observation Detections Table:
extent_code

The extent code in the per-observation detections table is defined identically to the extent code in the stacked observations detections table.


Manual Match Flag

Master Sources Table
man_match_flag

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.


Manual Source/Detection Addition Flag

Master Sources Table:
man_add_flag

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.

Stacked Observation Detections Table:
man_add_flag

The manual detection addition flag for a compact or extended (convex hull) detection is a Boolean that has a value of TRUE if the stacked observation detection was manually added to the catalog by human review. Otherwise, the value is FALSE.

Detections that are manually added must satisfy detection likelihood and other validity checks in order to appear in the final catalog. See also the Manual Source/Detection Inclusion Flag below.


Manual Source/Detection Inclusion Flag

Master Sources Table:
man_inc_flag

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.

Stacked Observation Detections Table:
man_inc_flag

The manual detection inclusion flag for a compact or extended (convex hull) detection is a Boolean that has a value of TRUE if the stacked observation detection was manually included in this catalog by human review. Otherwise, the value is FALSE.

Detections that are manually included are not required to satisfy detection likelihood or other validity checks. Manually included detections may or may not be manually added; if they are manually added then the man_add_flag will also be set to TRUE. See also the Manual Source/Detection Addition Flag above.


Manual Source/Detection Region Parameters Flag

Master Sources Table:
man_reg_flag

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.

Stacked Observation Detections Table:
man_reg_flag

The manual detection region parameters flag for a compact source is a Boolean that has a value of TRUE if any of the detection's region parameters (i.e., the source region ellipse semi-axes and/or rotation angle, and/or position that define the detection region evaluated by the maximum likelihood estimator [MLE]) were manually modified by human review. Otherwise, the value is FALSE.

The manual detection region parameters flag for an extended (convex hull) source is set to TRUE if the shape or position of the defining polygon was manually modified by human review. Otherwise, the value is FALSE.


Manual Source/Detection Position Flag

Master Sources Table:
man_pos_flag

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 flux-weighted centroid position by human review.

Stacked Observation Detections Table:
man_pos_flag

The manual detection position flag for a compact detection is a Boolean that has a value of TRUE if the final detection position was manually modified from the fitted position (determined by the maximum likelihood estimator [MLE]) were manually modified by human review. Otherwise, the value is FALSE.

The manual detection position flag for an extended (convex hull) detection is set to TRUE if the final detection position was manually modified from the flux-weighted centroid position by human review. Otherwise, the value is FALSE.


Multi-Chip Code

Stacked Observation Detections Table:
multi_chip_code

The multi-chip code for a compact or extended (convex hull) detection is a 16-bit coded integer that has all bits set to zero if the detection's position, source region, and background region do not dither between two or more chips (ACIS CCDs 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 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

Note that an extended (convex hull) detection (or associated background region) that extends across more than one chip by definition must dither across the chips.

Per-Observation Detections Table:
multi_chip_code

The multi-chip code in the per-observation detections table is defined identically to the edge code in the stacked observations detections table.


Pileup Warning Flag

Master Sources Table:
pileup_flag

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.

Stacked Observation Detections Table:
pileup_flag

The pileup warning flag for a compact detection is a Boolean that has a value of TRUE if the pileup fraction exceed ~10% for all contributing ACIS per-observation detections and energy bands. Otherwise, the value is FALSE.

The pileup warning flag for an extended (convex hull) detection is always NULL.

Per-Observation Detections Table:
pileup_warning

pileup_warning is a double precision value that reports the observed per-frame count rate of the brightest 3×3 pixel island in an ACIS detection's source region, averaged over the observation. This value may be correlated with pileup models to crudely estimate the pileup fraction for the detection. For the standard 3.2 sec ACIS frame time, the estimated pileup fraction is roughly equal to pileup_warning/2 for pileup_warning values ≲0.2.

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

pileup_warning for an extended (convex hull) detection is always NULL.


Saturated Source Flag

Master Sources Table:
sat_src_flag

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 piled-up, 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.

Stacked Observation Detections Table:
sat_src_flag

The saturated detection flag is for a compact detection is a Boolean that has a value of TRUE if all contributing observations are ACIS observations and all per-observation detections are significantly piled-up, i.e., sat_src_flag is TRUE for all of the contributing per-observation detections. Detection 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.

Per-Observation Detections Table:
sat_src_flag

The saturated detection flag for a compact detection is a Boolean that has a value of TRUE if the observation was obtained using ACIS and the detection is severely piled-up, to the extent that the source image may be flat-topped or have a central hole. Detection properties (including the value of pileup warning) are unreliable for all ACIS energy bands. Otherwise, the value is FALSE.

sat_src_flag for an extended (convex hull) source is always NULL.


Streak Source Flag

Master Sources Table:
streak_src_flag

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.

Stacked Observation Detections Table:
streak_src_flag

The streak detection flag for a compact detection is a Boolean that has a value of TRUE if all contributing observations are ACIS observations and all per-observation source regions overlap a defined region enclosing an identified readout streak, i.e., streak_src_flag is TRUE for all of the contributing per-observation detections. Otherwise, the value is FALSE.

The streak source flag for an extended (convex hull) detection is TRUE if any contributing observations are ACIS observations and any per-observation detection source region overlaps a defined region enclosing an identified readout streak . Otherwise, the value is FALSE.

Per-Observation Detections Table:
streak_src_flag

The streak detection flag for a compact detection 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 a defined region enclosing an identified readout streak. Otherwise, the value is FALSE.

The streak detection flag for an extended (convex hull) detection is TRUE if any part of the extended (convex hull) detection region overlaps a defined region enclosing an identified readout streak. Otherwise, the value is FALSE.


Variability Flag

Master Sources Table:
var_flag

The variability flag for a compact source is a Boolean that has a value of TRUE if variability is detected within any single observation or between any pair of contributing observations in any science energy band. Otherwise, the value is FALSE.

The variability flag for an extended (convex hull) source is always NULL.

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 for a compact detection is a 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 is 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.

The variability code for an extended (convex hull) detection is always NULL.


Inter-observation Variable Hardness Ratio Flag

Master Sources Table:
var_inter_hard_flag

The inter-observation 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 inter-observation variable hardness ratio flag for an extended (convex hull) source is always NULL.

Stacked Observation Detections Table:
var_inter_hard_flag

The inter-observation variable hardness ratio flag for a compact detection 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 values is FALSE.