M31CFCXO ivo://nasa.heasarc/m31cfcxo NASA/GSFC HEASARC Hofmann et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The central field of the Andromeda galaxy (M 31) was monitored from 2006 to 2012 using the Chandra HRC-I detector (about 0.1 - 10 keV energy range) with the main aim of detecting X-rays from optical novae. The authors present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Based on these observations, they studied the X-ray long-term variability of the source population and especially of the X-ray binaries in M31. The authors created a catalog of sources detected in the 64 available observations that adds up to a total exposure time of about 1 Ms. To study the variability, they developed a processing pipeline to derive long-term Chandra HRC-I light curves for each source over the 13 years of observations, and also searched for extended X-ray sources in the merged images. This table contains the point-source catalog of 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalog allows the authors to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts, as well as 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest that outburst sources are less frequent in globular clusters than in the field of M 31. Seven supernova remnants (not included in the point-source catalog) were detected, one of which is a new candidate, and also the first X-rays from a known radio supernova remnant were resolved. In addition to 33 known optical nova/X-ray source correlations, the authors discovered one previously unknown super-soft X-ray outburst and several new nova candidates. A large sample of detailed long-term X-ray light curves of sources in the M31 central field has been obtained in this study (see Appendix B.1 of the reference paper), which helps in understanding the X-ray population of our neighboring spiral galaxy M 31. Based on all the available Chandra HRC-I observations (see Table A.1 in the reference paper for the complete list), a source catalog has been created (available in this HEASARC table) and the energy flux of each source in every individual observation derived (these are not available in this HEASARC table, but are obtainable at the CDS: for more details, see the files <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A%2BA/555/A65/ReadMe">https://cdsarc.cds.unistra.fr/ftp/cats/J/A%2BA/555/A65/ReadMe</a> and <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz">https://cdsarc.cds.unistra.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz</a>). One thing to be aware of is that, in the latter file, upper limits are denoted by a '>' symbol rather than the more usual '<' symbol!). These fluxes were calculated assuming a generic power law spectrum and Galactic foreground absorption for each source. This table was created by the HEASARC in August 2013 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/555/A65">CDS catalog J/A+A/555/A65</a> files table1.dat and xcorr.dat. This is a service provided by NASA HEASARC . 2013A&A...555A..65H https://heasarc.gsfc.nasa.gov/W3Browse/all/m31cfcxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=m31cfcxo& GET text/xml 180 99999 true 10.64333 40.95401 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=m31cfcxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_m31cfcxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public m31cfcxo M 31 Central Field Chandra HRI X-Ray Point Source Catalog source_number Sequential Identification Number for Each Source in Catalog meta.id;src short nullable name Source Designation 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 count_rate Net Count Rate ct/s phot.count;em.X-ray double nullable count_rate_error Error in Net Count Rate ct/s stat.error;phot.count;em.X-ray double nullable lx Luminosity erg/s phys.luminosity;em.X-ray double nullable lx_error Luminosity Error erg/s stat.error;phys.luminosity;em.X-ray double nullable broad_type Broad Classification of Source src.class char nullable min_flux Minimum Flux erg/s/cm^2 phot.flux;em.X-ray;stat.min double nullable light_curve_class Light Curve Classification meta.code;src.var char nullable globular_cluster_name Globular Cluster Designation meta.id.assoc char nullable bck_counts Net Background Counts ct phot;instr.background;em.X-ray double nullable comments_and_refs Comments and References meta.note char nullable st_var_significance Highest svar Between Observations stat.likelihood;src.var;em.X-ray double nullable flux_error Flux Error erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable broad_type_flag Flag for Broad Classification of Source meta.code;src.class char nullable near_neighbor_offset Distance to Nearest Neighbor arcsec pos.angDistance double nullable bck_count_rate_error Error in Background Count Rate ct/s stat.error;phot.count;instr.background;em.X-ray double nullable nova_name Nova Designation meta.id.cross char nullable error_radius Positional Uncertainty arcsec stat.error;pos double nullable lt_var_significance Source Variability Parameter stat.likelihood;src.var;em.X-ray double nullable flux Flux in 0.2-10keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable counts Net Counts ct phot;em.X-ray double nullable max_to_min_ratio Highest Source Flux Ratio phot.flux;arith.ratio;em.X-ray double nullable min_flux_error Error of Minimum Flux erg/s/cm^2 stat.error;phot.flux;em.X-ray;stat.min double nullable counts_error Error in Net Counts ct stat.error;phot;em.X-ray double nullable bck_count_rate Background Count Rate ct/s phot.count;instr.background;em.X-ray double nullable detect_image_number Number of Detection Image meta.code;instr.pixel short nullable lii Galactic Longitude degree pos.galactic.lon double nullable bii Galactic Latitude degree pos.galactic.lat double nullable class Browse Object Classification src.class short nullable alt_names X-Ray Correlations meta.id.cross char nullable max_flux Maximum Flux erg/s/cm^2 phot.flux;em.X-ray;stat.max double nullable max_flux_error Error of Maximum Flux erg/s/cm^2 stat.error;phot.flux;em.X-ray;stat.max double nullable max_snr Highest Detection Significance stat.snr;em.X-ray double nullable exposure Exposure Time s time.duration;obs.exposure double nullable fraction_detections Ratio of Detections to Observations meta.code;obs;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