Master Sources Table

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model amplitude and the associated two-sided 68% confidence limits, proportional to the ratio of the blackbody emitting source radius, \(R\), and the distance to the source, \(d\). The amplitude is defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit blackbody model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed blackbody model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting blackbody model.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model temperature (kT) in units of keV and the associated two-sided 68% confidence limits.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit total equivalent neutral hydrogen column density, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed bremsstrahlung model fit, in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^-3 and \(D\) is the distance to the source in cm.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^-3 and \(D\) is the distance to the source in cm.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The best-fit bremsstrahlung model normalization and the associated two-sided 68% confidence limits. The model normalization is defined by:

where \(n_{e}\) and \(n_{i}\) are the electron and ion number densities, respectively, in cm^-3 and \(D\) is the distance to the source in cm.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The fit statistic defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting bremsstrahlung model.

From the Source Flags column descriptions page:

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.

From the Position and Position Errors column descriptions page:

The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'.

From the Source Flags column descriptions page:

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.

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

From the Position and Position Errors column descriptions page:

The statistically averaged source position uncertainties are expressed in the form of an error ellipse centered on the source position, projected from the celestial sphere onto a common tangent plane. The parameters specifying the geometry of the error ellipse are the radii of the semi-major and semi-minor axes (err_ellipse_r0, err_ellipse_r1), and the astronomical position angle of the major axis of the ellipse (err_ellipse_ang). The radii of the semi-major and semi-minor axes correspond to the 95% confidence intervals along these axes.

From the Source Flags column descriptions page:

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.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm².

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm².

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed blackbody model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, a blackbody temperature, and a blackbody model amplitude.

The blackbody flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed blackbody model, in units of erg/s/cm².

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm².

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm².

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed bremsstrahlung model is fit over the energy range 0.5-7.0 keV; the free parameters to be fitted are: a total equivalent neutral hydrogen absorbing column density, bremsstrahlung temperature, and bremsstrahlung model amplitude.

The bremsstrahlung flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fit absorbed bremsstrahlung model, in units of erg/s/cm².

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm².

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Aperture Model Energy Fluxes' section of the Source Fluxes column descriptions page:

The aperture model energy fluxes and associated two-sided confidence limits represent the best estimates of the power law, blackbody, bremsstrahlung, and APEC aperture model energy fluxes in the source region (flux_powlaw_aper, flux_bb_aper, flux_brems_aper, flux_apec_aper) and in an elliptical aperture that includes the 90% encircled counts fraction of the PSF at the source location (flux_powlaw_aper90, flux_bb_aper90, flux_brems_aper90, flux_apec_aper90), corrected by the PSF aperture fraction, livetime, and exposure.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm².

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model flux and the associated two-sided 68% confidence limits represent the integrated 0.5-7 keV flux derived from the best-fitting absorbed power law model, in units of erg/s/cm².

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Spectral Properties column descriptions page:

Hardness ratios appear in both the Master Sources Table and the Per-Observation Detections Table with the field names hard_xy, hard_xy_hilim, and hard_xy_lolim. The hardness ratios that appear in the Master Sources Table are determined from the Bayesian probability distribution functions (PDFs) of the aperture source photon fluxes derived from the source regions of the contributing individual source observations contained in the Per-Observation Detections Table. Only energy bands hard (h, 2.0-7.0 keV), medium (m, 1.2-2.0 keV) and soft (s, 0.5-1.2 keV) are used.

For two given energy bands, they are defined at the single observation level as the flux value in the softer band, subtracted from the flux value in the harder band, relative to their sum. However, since the PDFs are used, this definition is based on probabilistic considerations. Just like the fluxes are random variables with associated probabilities, so are the hardness ratios. Specifically, the values listed are the ones that maximize the following PDF:

By convention for the catalog, band x is always the higher energy band. As an example, hard_ms is the medium-to-soft band hardness ratio, defined as:

Note that this definition of hardness ratio is different than that used in Chandra Source Catalog Release 1, where the denominator in the ratio was obtained from combining all three energy bands: soft, medium, and hard.

As the reported values for each of these quantities represent the maximum a posteriori values of their given PDFs, the column hardness ratio values might differ slightly from that calculated directly from the aperture fluxes reported in the catalog.

Hardness ratios using the broad, ultra-soft, and HRC bands are not included in the catalog. The two-sided confidence limits associated with the ACIS hardness ratios are computed from the marginalized probability distributions and always lie within the range -1 to 1. If an aperture flux marginalized probability distribution cannot be computed for a given energy band, then no colors associated with that band are reported. At the stack and master level, the hardness ratios are also evaluated using the expressions above, but using respectively all the observations in the stack or best Bayesian block.

In Chandra Source Catalog Release 2, the individual source detection hardness ratios are also assessed for variability among the individual observations. See the description of Source Variability. A detailed description of hardness ratios can be found in the hardness ratios and variability memo.

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).

From the Source Significance column descriptions page:

The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood.

The fundamental metric used to decide whether a source is included in CSC 2.1 is the likelihood,

where \(P\) is the probability that an MLE fit to a point or extended source model, in a region with no source, would yield a change in fit statistic as large or larger than that observed, when compared to a fit to background only.

The likelihood is closely related to the probability, \(P_{\mathrm{Pois}}\), that a Poisson distribution with a mean background in the source aperture would produce at least the number of counts observed in the aperture. This quantity, called detect_significance, is also reported in CSC 2.1. Smoothed background maps are used to estimate mean background, and detect_significance is expressed in terms of the number of \(\sigma\), \(z\), in a zero-mean, unit standard deviation Gaussian distribution that would yield an upper integral probability \(P_{\mathrm{Gaus}}\), from \(z\) to \(\infty\), equivalent to \(P_{\mathrm{Pois}}\). That is,

where

From the Source Flags column descriptions page:

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.

From the Source Flags column descriptions page:

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.

From the Source Flags column descriptions page:

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.

From the Source Flags column descriptions page:

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.

From the Source Flags column descriptions page:

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.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the mean background-subtracted fluxes in the modified source region (photflux_aper_avg, flux_aper_avg) and in the modified elliptical aperture (photflux_aper90_avg, flux_aper90_avg), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for all source observations in which the master source was detected or in the field of view. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the 'Aperture Photometry Fluxes' section of the Source Fluxes column descriptions page:

Aperture photometry quantities are derived from counts in source regions or elliptical apertures, with background estimated from counts in surrounding background regions. Corrections are made for PSF aperture fractions, livetime, and exposure. In the case of energy fluxes, the conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon. For all aperture photometry quantities, a Bayesian statistical analysis is performed to determine background-marginalized posterior probability distribution for the flux quantity, and the mode and 68% percentiles of the distribution are reported as the flux value and confidence limits.

Fluxes are determined for each per-observation detection, for each stack, and for the master source. At the stack level, aperture data from all valid source observations in the stack are combined. At the master source level, a Bayesian Blocks analysis is performed to determine the sets of source observations consistent with a constant source flux. Aperture data from the set with the largest total exposure are then combined to determine master source 'best estimate' fluxes and confidence limits. In addition, aperture data from all source observations in which the master source was detected or in the field of view are combined to determine master source average fluxes and confidence limits.

The aperture source photon and energy fluxes and associated two-sided confidence limits represent the 'best estimate' background-subtracted fluxes in the modified source region (photflux_aper, flux_aper) and in the modified elliptical aperture (photflux_aper90, flux_aper90), corrected by the appropriate PSF aperture fractions, livetime, and exposure, for the Bayesian Block with the largest exposure. The conversion from photons s^-1 cm^-2 to ergs s^-1 cm^-2 is performed by summing the photon energies for each incident source photon and scaling by the local value of the ARF at the location of the incident photon.

From the Source Flags column descriptions page:

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.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm²/keV defined at 1 keV.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm²/keV defined at 1 keV.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit amplitude of the power law model and associated two-sided 68% confidence limits in units of photons/s/cm²/keV defined at 1 keV.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit power law photon index and the associated two-sided 68% confidence limits, \(\gamma\), defined as:

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The best-fit equivalent neutral hydrogen absorbing column, \(N_{H}\), and the associated two-sided 68% confidence limits from an absorbed power law model spectral fit in units of 10²⁰ cm^-2.

From the 'Spectral Model Fits' section of the Spectral Properties column descriptions page:

The master source spectral fit will use the ACIS observations contained in the best block provided the total summed background-subtracted counts for all of the observations is at least 150 counts in the 0.5-7.0 keV energy range. If this is the case then joint fits are made using power law, blackbody, bremsstrahlung, and apec models to the PI spectra extracted from the source region, with the final flux value and limits calculated using modelflux.

The absorbed power law model spectral fit is performed over the energy range 0.5-7.0 keV; the free parameters to be fitted are the total equivalent neutral hydrogen absorbing column density, power law photon index, and power law amplitude.

The power law model spectral fit statistic is defined as the value of the \(\chi^{2}\) (data variance) statistic per degree of freedom for the best-fitting absorbed power law model.

From the Position and Position Errors column descriptions page:

The equatorial coordinates of a source in the Master Sources Table are the best estimates of the ICRS celestial position of the source, determined by statistically averaging the positions of detections from the individual stacked observations that are uniquely matched (i.e., those that have match_type="u") to the source. The calculation of the averaged positions and position uncertainties is described in detail in the How and Why topic 'Source Position Errors in the Master Sources Table'.

From the Source Flags column descriptions page:

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.

From the Source Significance column descriptions page:

The maximum likelihood and flux significance across all stacked observations and energy bands are reported as the master source significance and likelihood.

Flux significance is a simple estimate of the ratio of the flux measurement to its average error. The mode of the marginalized probability distribution for photflux_aper is used as the flux measurement and the average error, \(\sigma_{e}\), is defined to be:

which are both used to estimate flux significance.

From the Source Flags column descriptions page:

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.

From the Source Flags column descriptions page:

The variability flag for a compact source is a Boolean that has a value of TRUE if variability is detected (the corresponding var_index value is ≥6) within any single observation or between any pair of observations contributing to the master source, in any science energy band. Otherwise, the value is FALSE.

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

From the Source Flags column descriptions page:

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.

From the Source Variability column descriptions page:

A Boolean set to FALSE if var_inter_hard_prob is below 0.3 for all three hardness ratios, and set to TRUE otherwise.

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

From the Source Variability column descriptions page:

The inter-observation spectral variability probability (var_inter_hard_prob) is a value that records the probability that the source region hardness ratios varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. The definition of this probability is identical to that of the inter-observation source variability (var_inter_prob), and also utilizes the same hypothesis rejection test, but based on the probability distributions (PDFs) for the hardness ratios, rather than the probability distributions for the fluxes. The definition of the hardness ratio PDFs can be found in the memo, and also in the hardness ratios columns page. High values of var_inter_hard_prob indicate that the source is spectrally variable in the corresponding combination of bands.

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

From the Source Variability column descriptions page:

Similarly to var_inter_sigma, the inter-observation hardness ratio variability parameter (var_inter_hard_sigma) is the absolute value of the difference between the error weighted mean of the source region hardness ratio PDF when a single hardness ratio is assumed, and the mean of the source region hardness ratio PDF for the individual observation that maximizes the absolute value of the difference:

Of all contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_hard_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation hardness ratios.

From the Source Variability column descriptions page:

The inter-observation variability index (var_inter_index) is an integer value in the range \([0,8]\) that is derived according to the estimated value of the quantity \(D/(N-1)\) defined above. It is used to evaluate whether the source region photon flux is constant between the observations. The degree of confidence in variability expressed by this index is similar to that of the intra-observation variability index. Below we tabulate the association between the value of \(D/(N-1)\) and inter-observation variability index.

From the Source Variability column descriptions page:

The inter-observation variability probability (var_inter_prob) is a value that records the probability that the source region photon flux varied between the contributing observations, based on the hypothesis rejection test described in the hardness ratios and variability memo. Given the \(N\) individual Bayesian probability distribution of the aperture fluxes for the same source in \(N\) different observations (their means and standard deviations), we estimate for each band the maximum likelihood \(\mathcal{L}_{1}^{\mathrm{max}}\) and the corresponding maximizing arguments \(F_{\left\langle band \right\rangle}^{i,\mathrm{max}}\), of the observed fluxes assuming a different flux for each observation, as well as the maximum likelihood \(\mathcal{L}_{2}^{\mathrm{max}}\) and the corresponding maximizing argument \(F_{\left\langle band \right\rangle}^{\mathrm{max}}\) of the observed fluxes assuming a single flux (the latter is the null hypothesis of no variability). As per Wilks' theorem, the quantity:

follows \(\chi^{2}\) distribution with \(N-1\) degrees of freedom, under the null hypothesis. Therefore, the null hypothesis (non-variability) is rejected with a probability proportional to the cumulative distribution of the \(\chi^{2}\) statistic for values smaller than the estimated \(D\). The quantity var_inter_prob represents this cumulative probability, and therefore gives the probability that the source is variable.

The reason for this careful definition is that the probabilities for intra-observation and inter-observation variability are, by necessity, of a different nature. Whereas one can say with reasonable certainty whether a source was variable during an observation covering a contiguous time interval, when comparing measured fluxes from different observations one knows nothing about the source's behavior during the intervening interval(s). Consequently, when the inter-observation variability probability is high (e.g., var_inter_prob > 0.7), one can confidently state that the source is variable on longer time scales, but when the probability is low, all one can say is that the observations are consistent with a constant flux.

From the Source Variability column descriptions page:

The inter-observation flux variability (var_inter_sigma) is the absolute value of the difference between the error weighted mean of the source region photon flux density PDF when a single flux is assumed \(\left( F_{\left\langle band \right\rangle}^{\mathrm{max}} \right)\), and the mean of the source region photon flux density PDF for the individual observation that maximizes the absolute value of the difference \(\left( F_{\left\langle band \right\rangle}^{i,\mathrm{max}} \right)\):

Of all the contributing observations, the observation that yields the highest value for this equation, is used in computing this value, which is recorded in var_inter_sigma. Intuitively, this quantity can be interpreted as the variance of the individual observation fluxes.

From the Source Variability column descriptions page:

The intra-observation variability index (var_intra_index) represents the highest value of the variability indices (var_index) calculated for each of the contributing observations.

From the Source Variability column descriptions page:

The Gregory-Loredo, Kolmogorov-Smirnov (K-S) test, and Kuiper's test intra-observation variability probabilities represent the highest values of the variability probabilities (var_prob, ks_prob, kp_prob) calculated for each of the contributing observations (i.e., the highest level of variability among the observations contributing to the master source entry).