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.
| Context | Column Name | Type | Units | Description |
|---|---|---|---|---|
| Source Name | 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.] | |
| Position and Position Errors | ra | double | deg | Source position, ICRS right ascension |
| dec | double | deg | Source position, ICRS declination | |
| 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 | |
| err_ellipse_ang | double | deg | position angle of the major axis of the 95% confidence level error ellipse | |
| gal_b | double | deg | Source position, galactic latitude | |
| gal_l | double | deg | Source position, galactic longitude | |
| Source Flags | 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 | |
| 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 | ||
| 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 | ||
| 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 | ||
| 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 | ||
| 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. | ||
| 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_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 | ||
| 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 | ||
| 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 | ||
| Source Extent and Errors | 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 | |
| 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 | |
| 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 | |
| Source Fluxes | For column names listed in this section, sources have at least one or as many as six filled (non-null) entries in the Master Source Catalog, corresponding to the six CSC energy bands (five ACIS bands, one HRC band). |
ACIS source detection energy bands (keV): B (0.5-7.0), S (0.5-1.2), M (1.2-2.0), H (2.0-7.0) ACIS science energy bands (keV): b (0.5-7.0), u (0.2-0.5), s (0.5-1.2), m (1.2-2.0), h (2.0-7.0) HRC source detection and science energy band (keV): ~0.1-10.0 |
||
| 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_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 | |
| 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 | |
| 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_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_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_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_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_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_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_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_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 | |
| Source Significance | significance | double | highest value of source flux significance among all science energy bands and contributing observations to the merged source entry | |
| Spectral Properties | 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 | ||
| alpha | double |
photon index (α, defined as FE~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 | ||
| 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_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" | |
| nh_powlaw | double | N HI atoms 1020 cm-2 | total neutral Hydrogen absorbing column density, NH, 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" | |
| 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 | |
| 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_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 | |
| nh_bb | double | N HI atoms 1020 cm-2 | total neutral Hydrogen absorbing column density, NH, 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, NH, in the direction of the source [determined from the interpolation data of Dickey and Lockman (1990; Ann. Rev. Astron. Astrophys., 28, 215)] | |
| Source Variability | 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). | |
| 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). | ||
| 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_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_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). | |
| 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_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_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). | |
| Observation Summary | acis_num | integer | total number of ACIS imaging observations contributing to the Master Source Catalog record of the source | |
| acis_hetg_num | integer | total number of 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_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 | ||
| 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_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 | ||
| hrc_num | integer | total number of HRC imaging observations contributing to the Master Source Catalog record of the source | ||
| hrc_hetg_num | integer | total number of 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_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 | ||
| 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_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 | ||