Stacked Observation Detections Table
The concept of Stacks are new to CSC 2.0, as discussed on the Catalog Organization page.
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.
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 |