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Each identified distinct X-ray source on the sky is represented in the catalog by one or more "stack detection" entries—one for each stack in which the source has been detected—and a single "master source" entry. The individual stack entries record all of the properties about a detection extracted from a single stack, as well as associated file-based data products, which are stack-specific.

Note: Source properties in the catalog which have a value for each science energy band (type "double[6]", "long[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 background-subtracted, aperture-corrected broad-band and hard-band energy fluxes, respectively.

Switch to: Columns listed alphabetically

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Context	Column Name	Type	Units	Description
Stack Identification	detect_stack_id			detect stack identifier (designation of observation stack used for source detection) in the format '{acis|hrc}fJhhmmsss{+|-}ddmmss_nnn'
	ra_stack			detect stack tangent plane reference position, ICRS right ascension
	dec_stack			detect stack tangent plane reference position, ICRS declination
Instrument Information	instrument	string		instrument used for the observation: 'ACIS' or 'HRC'
	grating	string		transmission grating used for the stacked observation: 'NONE', 'HETG', or 'LETG'
Processing Information	ascdsver	string		software version used to create the Level 3 detect stack event data file
	caldbver	string		calibration database version used to calibrate the Level 3 detect stack event data file
	crdate	string		creation date/time of the Level 3 detect stack event data file, UTC (yyyy-mm-ddThh:mm:ss)
Source Identification	region_id	integer		detection region identifier (component number)
Source Position and Position Errors	ra	double	deg	detection position, ICRS right ascension
	dec	double	deg	detection position, ICRS declination
	err_ellipse_r0	double	arcsec	major radius of the 95% confidence level position error ellipse
	err_ellipse_r1	double	arcsec	minor radius of the 95% confidence level position error ellipse
	err_ellipse_ang	double	deg	position angle (referenced from local true north) of the major axis 95% confidence level error ellipse
	theta_mean	double	arcmin	mean source region aperture off-axis angle from all stacked observations
Source Significance	flux_significance	double[6]		significance of the stacked-observation detection determined from the ratio of the stacked-observation detection photon flux to the estimated error in the photon flux, for each science energy band
	detect_significance	double[6]		significance of the stacked-observation detection computed by the stacked-observation detection algorithm for each science energy band
	likelihood	double[6]		log-likelihood of the stacked-observation detection computed by the Maximum Likelihood Estimator fit to the photon counts distribution for each science energy band
	likelihood_class	string		highest detection likelihood classification across all energy bands
Source Codes and Flags	conf_code	integer		compact detection may be confused (bit encoded: 1: background region overlaps another background region; 2: background region overlaps another source region; 4: source region overlaps another background region; 8: source region overlaps another source region; 256: compact detection is overlaid on an extended detection)
	dither_warning_flag	boolean		highest statistically significant peak in the power spectrum of the detection source region count rate occurs at the dither frequency or at a beat frequency of the dither frequency in one or more of the stacked observations
	edge_code	coded byte		detection position, or source or background region dithered off a detector boundary (chip pixel mask) during one or more of the stacked observations (bit encoded: 1: background region dithers off detector boundary; 2:source region dithers off detector boundary; 4: detection position dithers off detector boundary)
	extent_code	integer		detection is extended, or deconvolved compact detection extent is inconsistent with a point source at the 90% confidence level in one or more of the stacked observations and energy bands (bit encoded: 1, 2, 4, 8, 16, 32: deconvolved compact detection extent is not consistent with a point source in the ACIS ultrasoft, soft, medium, hard, broad, or HRC wide (~0.1-10.0 keV) energy band, respectively; 256: extended detection)
	multi_chip_code	coded byte		source position, or source or background region dithered multiple detector chips during one or more of the stacked observations (bit encoded: 1: background region dithers across 2 chips; 2: background region dithers across >2 chips; 4: source region dithers across 2 chips; 8: source region dithers across >2 chips; 16: detection position dithers across 2 chips; 32: detection position dithers across >2 chips)
	pileup_flag	boolean		ACIS pile-up fraction exceeds ~10% in any stacked observations; detection properties may be affected
	sat_src_flag	boolean		detection is saturated in all stacked observations (strong ACIS pileup); detection properties are unreliable
	streak_src_flag	boolean		detection located on an ACIS readout streak in all stacked observations; detection properties may be affected
	var_flag	boolean		detection displays flux variability within one or more of the stacked observations, or between stacked observations in one or more energy bands
	var_inter_hard_flag	boolean		detection hardness ratios are statistically inconsistent between two or more of the stacked observations
	man_add_flag	boolean		detection was manually added to the catalog via human review
	man_inc_flag	boolean		detection manually included to the catalog (detection was rejected by automated criteria)
	man_pos_flag	boolean		best fit detection position was manually modified via 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
Source Extent	major_axis	double[6]	arcsec	1σ radius along the major axis of the ellipse defining the deconvolved source extent for each science energy band
	major_axis_lolim	double[6]	arcsec	1σ radius along the major axis of the ellipse defining the deconvolved detection extent (68% lower confidence limit) for each science energy band
	major_axis_hilim	double[6]	arcsec	1σ radius along the major axis of the ellipse defining the deconvolved detection extent (68% upper confidence limit) for each science energy band
	minor_axis	double[6]	arcsec	1σ radius along the minor axis of the ellipse defining the deconvolved source extent for each science energy band
	minor_axis_lolim	double[6]	arcsec	1σ radius along the minor axis of the ellipse defining the deconvolved detection extent (68% lower confidence limit) for each science energy band
	minor_axis_hilim	double[6]	arcsec	1σ radius along the minor axis of the ellipse defining the deconvolved detection extent (68% upper confidence limit) for each science energy band
	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_lolim	double[6]	deg	position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved detection extent (68% lower confidence limit)
	pos_angle_hilim	double[6]	deg	position angle (referenced from local true north) of the major axis of the ellipse defining the deconvolved detection extent (68% upper confidence limit)
	src_area	double[6]	sq. arcseconds	area of the deconvolved detection extent ellipse, or area of the detection polygon for extended detections for each science energy band
Aperture Photometry	src_cnts_aper	double[6]	counts	aperture-corrected detection net counts inferred from the source region aperture for each science energy band
	src_cnts_aper_lolim	double[6]	counts	aperture-corrected detection net counts inferred from the source region aperture (68% lower confidence limit) for each science energy band
	src_cnts_aper_hilim	double[6]	counts	aperture-corrected detection net counts inferred from the source region aperture (68% upper confidence limit) for each science energy band
	src_rate_aper	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the source region aperture for each science energy band
	src_rate_aper_lolim	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the source region aperture (68% lower confidence limit) for each science energy band
	src_rate_aper_hilim	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the source region aperture (68% upper confidence limit) for each science energy band
	photflux_aper	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the source region aperture, calculated by counting X-ray events for ecach science energy band
	photflux_aper_lolim	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the source region aperture, calculated by counting X-ray events (68% lower confidence limit) for each science energy band
	photflux_aper_hilim	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the source region aperture, calculated by counting X-ray events (68% upper confidence limit) for each science energy band
	flux_aper	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the source region aperture, calculated by counting X-ray events for each science energy band
	flux_aper_lolim	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the source region aperture, calculated by counting X-ray events (68% lower confidence limit) for each science energy band
	flux_aper_hilim	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the source region aperture, calculated by counting X-ray events (68% upper confidence limit) for each science energy band
	src_cnts_aper90	double[6]	counts	aperture-corrected detection net counts inferred from the PSF 90% ECF aperture for each science energy band
	src_cnts_aper90_lolim	double[6]	counts	aperture-corrected detection net counts inferred from the PSF 90% ECF aperture (68% lower confidence limit) for each science energy band
	src_cnts_aper90_hilim	double[6]	counts	aperture-corrected detection net counts inferred from the PSF 90% ECF aperture (68% upper confidence limit) for each science energy band
	src_rate_aper90	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the PSF 90% ECF aperture for each science energy band
	src_rate_aper90_lolim	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the PSF 90% ECF aperture (68% lower confidence limit) for each science energy band
	src_rate_aper90_hilim	double[6]	counts s-1	aperture-corrected detection net count rate inferred from the PSF 90% ECF aperture (68% upper confidence limit) for each science energy band
	photflux_aper90	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events for each science energy band
	photflux_aper90_lolim	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events (68% lower confidence limit) for each science energy band
	photflux_aper90_hilim	double[6]	photons s-1 cm-2	aperture-corrected detection net photon flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events (68% upper confidence limit) for each science energy band
	flux_aper90	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events for each science energy band
	flux_aper90_lolim	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events (68% lower confidence limit) for each science energy band
	flux_aper90_hilim	double[6]	ergs s-1 cm-2	aperture-corrected detection net energy flux inferred from the PSF 90% ECF aperture, calculated by counting X-ray events (68% upper confidence limit) for each science energy band
Source Aperture	ra_aper	double	deg	center of the source region and background region apertures, ICRS right ascension
	dec_aper	double	deg	center of the source region and background region apertures, ICRS declination
	mjr_axis_aper	double	arcsec	semi-major axis of the elliptical source region aperture
	mnr_axis_aper	double	arcsec	semi-minor axis of the elliptical source region aperture
	pos_angle_aper	double	deg	position angle (referenced from local true north) of the semi-major axis of the elliptical source region aperture
	mjr_axis1_aperbkg	double	arcsec	semi-major axis of the inner ellipse of the annular background region aperture
	mnr_axis1_aperbkg	double	arcsec	semi-minor axis of the inner ellipse of the annular background region aperture
	mjr_axis2_aperbkg	double	arcsec	semi-major axis of the outer ellipse of the annular background region aperture
	mnr_axis2_aperbkg	double	arcsec	semi-minor axis of the outer ellipse of the annular background region aperture
	pos_angle_aperbkg	double	deg	position angle (referenced from local true north) of the semi-major axes of the annular background region aperture
	phot_nsrcs	integer[6]		number of detections fit simultaneously to compute aperture photometry quantities
Hardness Ratios	hard_hm	double		ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio
	hard_hm_lolim	double		ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio (68% lower confidence limit)
	hard_hm_hilim	double		ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio (68% upper confidence limit)
	var_inter_hard_prob_hm	double		inter-stacked-observation ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio variability probability
	var_inter_hard_sigma_prob_hm	double		inter-stacked-observation ACIS hard (2.0-7.0 keV) - medium (1.2-2.0 keV) energy band hardness ratio variability standard deviation
	hard_hs	double		ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio
	hard_hs_lolim	double		ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% lower confidence limit)
	hard_hs_hilim	double		ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% upper confidence limit)
	var_inter_hard_prob_hs	double		inter-stacked-observation ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability probability
	var_inter_hard_sigma_prob_hs	double		inter-stacked-observation ACIS hard (2.0-7.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability standard deviation
	hard_ms	double		ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio
	hard_ms_lolim	double		ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio (68% lower confidence limit)
	hard_ms_hilim	double		ACIS medium (1.2-2.0 keV)- soft (0.5-1.2 keV) energy band hardness ratio (68% upper confidence limit)
	var_inter_hard_prob_ms	double		inter-stacked-observation ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability probability
	var_inter_hard_sigma_prob_ms	double		inter-stacked-observation ACIS medium (1.2-2.0 keV) - soft (0.5-1.2 keV) energy band hardness ratio variability standard deviation
Temporal Variability	var_intra_index	integer[6]		intra-observation Gregory-Loredo variability index in the range [0, 10]: indicates whether the source region photon flux is constant within an observation (highest value across all stacked observations) for each science energy band
	var_intra_prob	double[6]		intra-observation Gregory-Loredo variability probability (highest value across all stacked observations for each science energy band
	ks_intra_prob	double[6]		intra-observation Kolmogorov-Smirnov test variability probability (highest value across all observations) for each science energy band
	kp_intra_prob	double[6]		intra-observation Kuiper's test variability probability (highest value across all stacked observations) for each science energy band
	var_inter_index	integer[6]		inter-stacked-observation variability index in the range [0, 10]: indicates whether the source region photon flux is constant between observations for each science energy band
	var_inter_prob	double[6]		inter-stacked observation variability probability, calculated from the χ2 distribution of the photon fluxes of the individual observations for each science energy band
	var_inter_sigma	double[6]	photons s-1 cm-2	inter-stacked-observation flux variability standard deviation; the spread of the individual observation photon fluxes about the error weighted mean for each science energy band
Timing Information	livetime	double	s	effective stacked observation exposure time, after applying the good time intervals and deadtime correction factor; vignetting and dead area corrections are NOT applied