Master Sources Table

Each distinct X-ray source identified on the sky is represented in the catalog by a single "master source" entry and one or more "source observation" entries, one for each observation in which the source has been detected. The master source entry records the best estimates of the properties of a source, based on the data extracted from the set of observations in which the source has been detected.

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 background-subtracted, aperture-corrected broad-band and hard-band energy fluxes, respectively.

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Column Name	Type	Units	Description
acis_hetg_num	integer		total number of ACIS/HETG observations contributing to the Master Source Catalog record of the source
acis_hetg_time	double		total ACIS/HETG observation exposure time (seconds of good time) for all ACIS/HETG observations contributing to the Master Source Catalog record of the source
acis_letg_num	integer		total number of ACIS/LETG observations contributing to the Master Source Catalog record of the source
acis_letg_time	double		total ACIS/LETG observation exposure time (seconds of good time) for all ACIS/LETG observations contributing to the Master Source Catalog record of the source
acis_num	integer		total number of ACIS imaging observations contributing to the Master Source Catalog record of the source
acis_time	double		total ACIS imaging exposure time (seconds of good time) for all ACIS imaging observations contributing to the Master Source Catalog record of the source
alpha	double		photon index (α, defined as F_E~E^{- α}) for best-fit power-law model spectral fit to the PI event data extracted from the source region
alpha_hilim	double		upper confidence limit for alpha
alpha_lolim	double		lower confidence limit for alpha
conf_flag	Boolean		Indicates that source is in a confused region. FALSE - the source detection region is not confused [i.e. not found to contain multiple sources, does not overlap other source detection regions, and contains no overlapping source ellipses in all contributing observations]; otherwise, TRUE
dec	double	deg	Source position, ICRS declination
err_ellipse_ang	double	deg	position angle of the major axis of the 95% confidence level error ellipse
err_ellipse_r0	double	arcseconds	major radius of the 95% confidence level error ellipse of the source position
err_ellipse_r1	double	arcseconds	minor radius of the 95% confidence level error ellipse of the source position
extent_flag	Boolean		Indicates an extended source. TRUE - 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, FALSE
flux_aper	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in the source region using the `direct' flux algorithm
flux_aper90	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in the elliptical aperture that includes the 90% Encircled Counts Fraction of the PSF at the source location, using the `direct' flux algorithm
flux_aper90_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits for "flux_aper90" values
flux_aper90_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits for "flux_aper90" values
flux_aper_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits for "flux_aper" values
flux_aper_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits for "flux_aper" values
flux_bb	double	ergs s^-1 cm^-2	integrated 0.5-7.0 keV flux of the best-fitting blackbody model spectral fit
flux_bb_aper	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in the source region by scaling a fixed blackbody spectral model
flux_bb_aper90	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in an elliptical aperture that includes the 90% Encircled Counts Fraction of the PSF at the source location, by scaling a fixed blackbody spectral model
flux_bb_aper90_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits on "flux_bb_aper90" values
flux_bb_aper90_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits on "flux_bb_aper90" values
flux_bb_aper_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits on "flux_bb_aper" values
flux_bb_aper_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits on "flux_bb_aper" values
flux_bb_hilim	double	ergs s^-1 cm^-2	upper confidence limit on flux_bb
flux_bb_lolim	double	ergs s^-1 cm^-2	lower confidence limit on flux_bb
flux_powlaw	double	ergs s^-1 cm^-2	integrated 0.5-7.0 keV energy flux for best fit power-law model spectral fit to the PI event data extracted from the source region
flux_powlaw_aper	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in the source region by scaling a fixed power-law spectral model
flux_powlaw_aper90	double[6]	ergs s^-1 cm^-2	background-subtracted, aperture-corrected energy fluxes for each science energy band, calculated from counts in an elliptical aperture that includes the 90% Encircled Counts Fraction of the PSF at the source location by scaling a fixed power-law spectral model
flux_powlaw_aper90_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits on "flux_powlaw_aper90" values
flux_powlaw_aper90_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits on "flux_powlaw_aper90" values
flux_powlaw_aper_hilim	double[6]	ergs s^-1 cm^-2	upper confidence limits on "flux_powlaw_aper" values
flux_powlaw_aper_lolim	double[6]	ergs s^-1 cm^-2	lower confidence limits on "flux_powlaw_aper" values
flux_powlaw_hilim	double	ergs s^-1 cm^-2	upper confidence limit on "flux_powlaw"
flux_powlaw_lolim	double	ergs s^-1 cm^-2	lower confidence limit on "flux_powlaw"
gal_b	double	deg	Source position, galactic latitude
gal_l	double	deg	Source position, galactic longitude
hard_xy	double[3]		hardness ratio for a pair of ACIS science energy bands, where x and y represent the higher (harder) and lower (softer) energy band designations, respectively.
hard_xy_hilim	double[3]		upper confidence limit on ''hard_xy'' value
hard_xy_lolim	double[3]		lower confidence limit on ''hard_xy'' value
hrc_hetg_num	integer		total number of HRC/HETG observations contributing to the Master Source Catalog record of the source
hrc_hetg_time	double		total HRC/HETG observation exposure time (seconds of good time) for all HRC/HETG observations contributing to the Master Source Catalog record of the source
hrc_letg_num	integer		total number of HRC/LETG observations contributing to the Master Source Catalog record of the source
hrc_letg_time	double		total HRC/LETG observation exposure time (seconds of good time) for all HRC/LETG observations contributing to the Master Source Catalog record of the source
hrc_num	integer		total number of HRC imaging observations contributing to the Master Source Catalog record of the source
hrc_time	double		total HRC imaging exposure time (seconds of good time) for all HRC imaging observations contributing to the Master Source Catalog record of the source
kp_intra_prob	double[6]		Intra-observation Kuiper's test variability probability, i.e. probability that the source is variable within an observation, in each of the science energy bands, using Kuiper's test. (Highest value among contributing observations used).
ks_intra_prob	double[6]		Intra-observation Kolmogorov-Smirnov variability probability, i.e. probability that the source is variable within an observation, in each of the science energy bands, using the K-S test. (Highest value among contributing observations used).
kt	double	keV	temperature of the best-fitting blackbody model spectral fit to the PI event data extracted from the source region
kt_hilim	double	keV	upper confidence limit on kt
kt_lolim	double	keV	lower confidence limit on kt
major_axis	double	arcseconds	1σ radius along the major axis of the ellipse defining the deconvolved source extent
major_axis_err	double	arcseconds	Error on the deconvolved source extent major axis
man_inc_flag	Boolean		Indicates a source identified manually (automatic detection failed). TRUE - the source region was manually included in all of the contributing observations by human review; otherwise, FALSE
man_match_flag	Boolean		Indicates that source observations were manually merged. TRUE - the set of individual source observations contributing to the current master source observation region was manually selected and modified by human review; otherwise, FALSE
man_reg_flag	Boolean		Indicates that source parameters were manually adjusted due to pileup. TRUE - the source region parameters were manually modified in all of the contributing observations by human review [in the event of extreme pile-up]; otherwise, FALSE
minor_axis	double	arcseconds	1σ radius along the minor axis of the ellipse defining the deconvolved source extent
minor_exis_err	double	arcseconds	Error on the deconvolved source extent minor axis
name	string		source name in the form "CXO Jhhmmss.s+ddmmss" [Chandra source names use the ICRS position to an accuracy of 0.1s in RA and 1.0s in Dec.]
nh_bb	double	N _HI atoms 10²⁰ cm^-2	total neutral Hydrogen absorbing column density, N_H, derived from the best-fitting thermal (black body) model spectral fits to the PI event data extracted from the source region
nh_bb_hilim	double	N _HI atoms 10²⁰ cm^-2	upper confidence limit on nh_bb
nh_bb_lolim	double	N _HI atoms 10²⁰ cm^-2	lower confidence limit on nh_bb
nh_gal	double	N _HI atoms 10²⁰ cm^-2	Galactic neutral Hydrogen column density, N_H, in the direction of the source [determined from the interpolation data of Dickey and Lockman (1990; Ann. Rev. Astron. Astrophys., 28, 215)]
nh_powlaw	double	N _HI atoms 10²⁰ cm^-2	total neutral Hydrogen absorbing column density, N_H, of the best fitting power-law model spectral fit to the PI event data extracted from the source region
nh_powlaw_hilim	double	N _HI atoms 10²⁰ cm^-2	upper confidence limit on "nh_powlaw"
nh_powlaw_lolim	double	N _HI atoms 10²⁰ cm^-2	lower confidence limit on "nh_powlaw"
photflux_aper	double[6]	photons s^-1 cm^-2	background-subtracted, aperture-corrected photon fluxes for each science energy band, calculated from counts in the source region using the `direct' flux algorithm
photflux_aper90	double[6]	photons s^-1 cm^-2	background-subtracted, aperture-corrected photon fluxes for each science energy band, calculated from counts in the elliptical aperture that includes the 90% Encircled Counts Fraction of the PSF at the source location using the `direct' flux algorithm
photflux_aper90_hilim	double[6]	photons s^-1 cm^-2	upper confidence limits for "photflux_aper90" values
photflux_aper90_lolim	double[6]	photons s^-1 cm^-2	lower confidence limits for "photflux_aper90" values
photflux_aper_hilim	double[6]	photons s^-1 cm^-2	upper confidence limits for "photflux_aper" values
photflux_aper_lolim	double[6]	photons s^-1 cm^-2	lower confidence limits for "photflux_aper" values
pileup_flag	Boolean		Indicates that the source properties may be affected by ACIS pileup. FALSE - the pileup fraction does not exceed ~10% for all contributing ACIS observations and source detection energy bands; otherwise, TRUE
pos_angle	double	deg	position angle of the major axis of the ellipse defining the deconvolved source extent
pos_angle_err	double	deg	Error on the deconvolved source extent position angle
ra	double	deg	Source position, ICRS right ascension
sat_src_flag	Boolean		Indicates a saturated source (strong ACIS pileup). TRUE - all of the contributing observations are ACIS observations that are significantly piled-up [to the extent that the source image may be flattened or have a central hole]; otherwise, FALSE.
significance	double		highest value of source flux significance among all science energy bands and contributing observations to the merged source entry
streak_src_flag	Boolean		Indicates that source lies on an ACIS readout streak. TRUE - all of the contributing observations are ACIS observations and contain source regions that overlap a defined region enclosing an identified readout streak; otherwise, FALSE
var_flag	Boolean		FALSE - variability is not detected within any single observation or between any pair of observations, in any science energy band; otherwise, TRUE
var_inter_hard_flag	Boolean		Indicates that the source hardness ratios are variable. TRUE - the hardness ratios of at least one of the contributing individual source observations are statistically inconsistent with the corresponding hardness ratios of all of the other contributing individual source observations; otherwise, FALSE
var_inter_index	integer[6]		Inter-observation variability index in the range [0,10] that indicates if the source region photon flux is constant between the contributing observations, in each of the science energy bands.
var_inter_prob	double[6]		Inter-observation source variability probability, i.e. the probability that the source region photon flux varied between the contributing observations, in each of the science energy bands, using the χ² distribution of the photon fluxes and the standard deviations of the individual observations.
var_inter_sigma	double[6]	photons s^-1 cm^-2	Inter-observation flux variability, i.e. the spread of the source region photon flux densities of the individual observations about the error weighted mean source region photon flux density, in each of the science energy bands. (Highest value of flux variability among contributing observations used).
var_intra_index	integer[6]		Intra-observation variability index in the range [0,10] that indicates if the source region flux is uniform throughout an observation, in each of the science energy bands, using a Gregory-Loredo analysis. (Highest value among contributing observations used).
var_intra_prob	double[6]		Intra-observation Gregory-Loredo variability probability, i.e. probability that the source is variable within an observation, in each of the science energy bands, using a Gregory-Loredo analysis. (Highest value among contributing observations used).
var_intra_sigma	double[6]	counts s^-1	Intra-observation flux variability, i.e. the appropriately scaled count rate variability ("var_sigma"), in each of the science energy bands, using a Gregory-Loredo analysis. (Highest value among contributing observations used).