M 31 Disk Chandra PHAT Survey: X-Ray Source Catalog M31PHATCXO ivo://nasa.heasarc/m31phatcxo NASA/GSFC HEASARC Williams et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The X-ray source populations within galaxies are typically difficult to identify and classify with X-ray data alone. The authors break through this barrier by combining deep new Chandra ACIS-I observations with extensive Hubble Space Telescope (HST) imaging from the Panchromatic Hubble Andromeda Treasury (PHAT) of the M 31 disk. They detect 373 X-ray sources down to 0.35-8.0keV flux of 10<sup>-15</sup>erg/cm<sup>-2</sup>/s over 0.4deg<sup>2</sup>, 170 of which are reported for the first time. The authors identify optical counterpart candidates for 188 of the 373 sources, after using the HST data to correct the absolute astrometry of our Chandra imaging to 0.1". While 58 of these 188 are associated with point sources potentially in M 31, over half (107) of the counterpart candidates are extended background galaxies, 5 are star clusters, 12 are foreground stars, and 6 are supernova remnants. Sources with no clear counterpart candidate are most likely to be undetected background galaxies and low-mass X-ray binaries in M 31. The hardest sources in the 1-8keV band tend to be matched to background galaxies. The 58 point sources that are not consistent with foreground stars are bright enough that they could be high-mass stars in M 31; however, all but 8 have optical colors inconsistent with single stars, suggesting that many could be background galaxies or binary counterparts. For point-like counterparts, the authors examine the star formation history of the surrounding stellar populations to look for a young component that could be associated with a high-mass X-ray binary. The associated star formation histories for sources in the catalog are available in the linked table <a href="/W3Browse/chandra/m31phatsfh.html">M31PHATSFH</a>. In 2015 October, the authors observed the Panchromatic Hubble Andromeda Treasury (PHAT) footprint with Chandra with 7 pointings. The footprints are overlaid on a GALEX NUV image of M 31, along with the corresponding HST coverage, in Figure 1 of the reference paper. At each pointing they observed for about 50ks in VF mode (Chandra ObsID 17008 to 17014 spanning 2015 Oct 06 to 2015 Oct 26). This table was created by the HEASARC in April 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/239/13">CDS Catalog J/ApJS/239/13</a> file table4.dat and table6.dat. This is a service provided by NASA HEASARC . 2018ApJS..239...13W https://heasarc.gsfc.nasa.gov/W3Browse/all/m31phatcxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=m31phatcxo& GET text/xml 180 99999 true 11.18614 41.265105 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=m31phatcxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_m31phatcxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 HST 0.0166666666666667 Optical X-ray public m31phatcxo M 31 Disk Chandra PHAT Survey: X-Ray Source Catalog source_number Unique Sequential Identification Number for Each Source in the Catalog meta.id;src short nullable obsid Observation in Which Source Was Measured meta.id;obs int nullable name Catalog Source Designation ([WLP2018] CXO JHHMMSS.ss+DDMMSS.s) meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius X-Ray Position Uncertainty arcsec stat.error;pos double nullable b1_flux Energy Flux in 0.35-8.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b1_flux_neg_err Negative Uncertainty for Energy Flux in 0.35-8.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b1_flux_pos_err Positive Uncertainty for Energy Flux in 0.35-8.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b3_flux Energy Flux in 0.5-8.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b3_flux_neg_err Negative Uncertainty for Energy Flux in 0.5-8.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b3_flux_pos_err Positive Uncertainty for Energy Flux in 0.5-8.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable source_type Source Classification in Stiele+ 2011, J/A+A/534/A55 src.class char nullable b4_counts_pos_err Positive Uncertainty for Source Net Counts in 0.5-1.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b5_count_rate_neg_err Negative Uncertainty for Count Rate in 1.0-2.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b8_count_rate_limit Limit Flag for Count Rate in 4.0-8.0keV Band meta.code;phot.count;em.X-ray char nullable b6_counts Source Net Counts in 2.0-4.0keV Band ct phot.count;em.X-ray double nullable b8_flux Energy Flux in 4.0-8.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable optical_dec HST PHAT Declination degree pos.eq.dec;em.opt double nullable b3_counts_neg_err Negative Uncertainty for Source Net Counts in 0.5-8.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b8_counts_limit Limit Flag for Source Net Counts in 4.0-8.0keV Band meta.code;phot.count;em.X-ray char nullable b5_counts_neg_err Negative Uncertainty for Source Net Counts in 1.0-2.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b1_count_rate_neg_err Negative Uncertainty for Count Rate in 0.35-8.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b8_flux_pos_err Positive Uncertainty for Energy Flux in 4.0-8.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b9_flux_neg_err Negative Uncertainty for Energy Flux in 0.2-4.5keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b2_count_rate ARF-Corrected Count Rate in 0.35-2.0keV Band ct/s phot.count;em.X-ray double nullable b6_count_rate_limit Limit Flag for Count Rate in 2.0-4.0keV Band meta.code;phot.count;em.X-ray char nullable b7_count_rate_neg_err Negative Uncertainty for Count Rate in 2.0-8.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b4_flux_neg_err Negative Uncertainty for Energy Flux in 0.5-1.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b8_counts_neg_err Negative Uncertainty for Source Net Counts in 4.0-8.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b5_counts_pos_err Positive Uncertainty for Source Net Counts in 1.0-2.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b2_flux Energy Flux in 0.35-1.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b8_count_rate_pos_err Positive Uncertainty for Count Rate in 4.0-8.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable b2_counts_pos_err Positive Uncertainty for Source Net Counts in 0.35-1.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b2_counts_neg_err Negative Uncertainty for Source Net Counts in 0.35-1.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b2_count_rate_limit Limit Flag for Count Rate in 0.35-2.0keV Band meta.code;phot.count;em.X-ray char nullable hst_f160w_mag HST/WFC3 F160W Band Magnitude mag phot.mag;em.IR.H double nullable notes Notes from Visual Inspection of PHAT Images meta.note char nullable b1_counts Source Net Counts in 0.35-8.0keV Band ct phot.count;em.X-ray double nullable b7_counts_neg_err Negative Uncertainty for Source Net Counts in 2.0-8.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b5_counts_limit Limit Flag for Source Net Counts in 1.0-2.0keV Band meta.code;phot.count;em.X-ray char nullable b4_count_rate_pos_err Positive Uncertainty for Count Rate in 0.5-1.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable b4_count_rate_limit Limit Flag for Count Rate in 0.5-1.0keV Band meta.code;phot.count;em.X-ray char nullable source_flag Flag Indicates Note Concerning Source meta.code;src char nullable b8_counts Source Net Counts in 4.0-8.0keV Band ct phot.count;em.X-ray double nullable b2_flux_pos_err Positive Uncertainty for Energy Flux in 0.35-1.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b5_flux Energy Flux in 1.0-2.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b8_count_rate_neg_err Negative Uncertainty for Count Rate in 4.0-8.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b8_flux_limit Limit Flag for Energy Flux in 4.0-8.0keV Band meta.code;phot.flux;em.X-ray char nullable vmag_extinction Mean Extinction from Maps of Dalcanton+ (2015ApJ...814....3D) mag phys.absorption;em.opt.V double nullable b5_flux_neg_err Negative Uncertainty for Energy Flux in 1.0-2.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b2_counts Source Net Counts in 0.35-1.0keV Band ct phot.count;em.X-ray double nullable b6_counts_pos_err Positive Uncertainty for Source Net Counts in 2.0-4.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b6_flux_limit Limit Flag for Energy Flux in 2.0-4.0keV Band meta.code;phot.flux;em.X-ray char nullable b8_counts_pos_err Positive Uncertainty for Source Net Counts in 4.0-8.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable bii Galactic Latitude degree pos.galactic.lat double nullable prob_no_src Probability No Source Detected at This Location in 0.35-8.0keV Band percent stat.probability double nullable b7_flux_pos_err Positive Uncertainty for Energy Flux in 2.0-8.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b2_flux_limit Limit Flag for Energy Flux in 0.35-1.0keV Band meta.code;phot.flux;em.X-ray char nullable b7_flux_neg_err Negative Uncertainty for Energy Flux in 2.0-8.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b5_counts Source Net Counts in 1.0-2.0keV Band ct phot.count;em.X-ray double nullable b3_count_rate_pos_err Positive Uncertainty for Count Rate in 0.5-8.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable hst_f336w_mag HST/WFC3 F336W Band Magnitude mag phot.mag;em.opt.U double nullable b3_counts_pos_err Positive Uncertainty for Source Net Counts in 0.5-8.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable off_axis Off-Axis Angle in Chandra Observation arcmin instr.offset double nullable b8_count_rate ARF-Corrected Count Rate in 4.0-8.0keV Band ct/s phot.count;em.X-ray double nullable b4_count_rate ARF-Corrected Count Rate in 0.5-1.0keV Band ct/s phot.count;em.X-ray double nullable b9_flux_pos_err Positive Uncertainty for Energy Flux in 0.2-4.5keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b7_count_rate_limit Limit Flag for Count Rate in 2.0-8.0keV Band meta.code;phot.count;em.X-ray char nullable b5_flux_pos_err Positive Uncertainty for Energy Flux in 1.0-2.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b7_flux Energy Flux in 2.0-8.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b6_count_rate_pos_err Positive Uncertainty for Count Rate in 2.0-4.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable b3_count_rate_neg_err Negative Uncertainty for Count Rate in 0.5-8.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable phat_flag Flag Indicates PHAT Counterpart Code meta.code.class char nullable b7_flux_limit Limit Flag for Energy Flux in 2.0-8.0keV Band meta.code;phot.flux;em.X-ray char nullable optical_ra HST PHAT Right Ascension degree pos.eq.ra;em.opt double nullable hst_f475w_mag HST/ACS F475W Band Magnitude mag phot.mag;em.opt.B double nullable b3_counts Source Net Counts in 0.5-8.0keV Band ct phot.count;em.X-ray double nullable b4_count_rate_neg_err Negative Uncertainty for Count Rate in 0.5-1.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b2_count_rate_neg_err Negative Uncertainty for Count Rate in 0.35-1.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b1_counts_pos_err Positive Uncertainty for Source Net Counts in 0.35-8.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b7_counts Source Net Counts in 2.0-8.0keV Band ct phot.count;em.X-ray double nullable b4_counts_neg_err Negative Uncertainty for Source Net Counts in 0.5-1.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b1_count_rate ARF-Corrected Count Rate in 0.35-8.0keV Band ct/s phot.count;em.X-ray double nullable b5_count_rate_limit Limit Flag for Count Rate in 1.0-2.0keV Band meta.code;phot.count;em.X-ray char nullable b5_count_rate ARF-Corrected Count Rate in 1.0-2.0keV Band ct/s phot.count;em.X-ray double nullable b4_counts_limit Limit Flag for Source Net Counts in 0.5-1.0keV Band meta.code;phot.count;em.X-ray char nullable b2_counts_limit Limit Flag for Source Net Counts in 0.35-1.0keV Band meta.code;phot.count;em.X-ray char nullable b8_flux_neg_err Negative Uncertainty for Energy Flux in 4.0-8.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable class Browse Object Classification src.class short nullable b9_flux Energy Flux in 0.2-4.5keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b2_flux_neg_err Negative Uncertainty for Energy Flux in 0.35-1.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b3_count_rate ARF-Corrected Count Rate in 0.5-8.0keV Band ct/s phot.count;em.X-ray double nullable b4_flux_limit Limit Flag for Energy Flux in 0.5-1.0keV Band meta.code;phot.flux;em.X-ray char nullable b6_counts_limit Limit Flag for Source Net Counts in 2.0-4.0keV Band meta.code;phot.count;em.X-ray char nullable b5_flux_limit Limit Flag for Energy Flux in 1.0-2.0keV Band meta.code;phot.flux;em.X-ray char nullable b6_flux Energy Flux in 2.0-4.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable b6_counts_neg_err Negative Uncertainty for Source Net Counts in 2.0-4.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b7_counts_pos_err Positive Uncertainty for Source Net Counts in 2.0-8.0keV Band ct stat.error;stat.max;phot.count;em.X-ray double nullable b7_count_rate_pos_err Positive Uncertainty for Count Rate in 2.0-8.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable sph2011_source_number Matched Source Identifier in Stiele+ 2011, J/A+A/534/A55 meta.id.cross short nullable hst_f814w_mag HST/ACS F814W Band Magnitude mag phot.mag;em.opt.I double nullable b6_count_rate_neg_err Negative Uncertainty for Count Rate in 2.0-4.0keV Band ct/s stat.error;stat.min;phot.count;em.X-ray double nullable b7_counts_limit Limit Flag for Source Net Counts in 2.0-8.0keV Band meta.code;phot.count;em.X-ray char nullable b4_flux_pos_err Positive Uncertainty for Energy Flux in 0.5-1.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable b6_flux_neg_err Negative Uncertainty for Energy Flux in 2.0-4.0keV Band erg/s/cm^2 stat.error;stat.min;phot.flux;em.X-ray double nullable b5_count_rate_pos_err Positive Uncertainty for Count Rate in 1.0-2.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable b6_count_rate ARF-Corrected Count Rate in 2.0-4.0keV Band ct/s phot.count;em.X-ray double nullable b2_count_rate_pos_err Positive Uncertainty for Count Rate in 0.35-1.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable hst_f275w_mag HST mag phot.mag;em.UV.200-300nm double nullable b6_flux_pos_err Positive Uncertainty for Energy Flux in 2.0-4.0keV Band erg/s/cm^2 stat.error;stat.max;phot.flux;em.X-ray double nullable hst_f110w_mag HST/WFC3 F110W Band Magnitude mag phot.mag;em.IR.J double nullable b4_flux Energy Flux in 0.5-1.0keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable alt_name Alternative Source Designation Based on Source Number ([WLP2018] NNN) meta.id;src char nullable b1_count_rate_pos_err Positive Uncertainty for Count Rate in 0.35-8.0keV Band ct/s stat.error;stat.max;phot.count;em.X-ray double nullable b1_counts_neg_err Negative Uncertainty for Source Net Counts in 0.35-8.0keV Band ct stat.error;stat.min;phot.count;em.X-ray double nullable b7_count_rate ARF-Corrected Count Rate in 2.0-8.0keV Band ct/s phot.count;em.X-ray double nullable lii Galactic Longitude degree pos.galactic.lon double nullable b4_counts Source Net Counts in 0.5-1.0keV Band ct phot.count;em.X-ray double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable