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Description
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="ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/555/A65/ReadMe">ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/555/A65/ReadMe</a> and <a href="ftp://cdsarc.u-strasbg.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz">ftp://cdsarc.u-strasbg.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 .
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