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Description
This catalog is the complete ROSAT PSPC Source List of X-ray sources found in two surveys of M 31 reported by Supper et al. (1997, 2001). These papers reported the results of the analysis of the two ROSAT PSPC surveys of M 31 performed in the summers of 1991 and 1992, respectively. summer 1992. Supper et al. (2001) compare and combine the results from the two surveys. In the first survey, 396 X-ray point sources were detected, and an identical number in the second survey, although this equality is coincidental, as the source lists are different and contain only 239 sources in common. Within the approximately 10.7 square degrees field of view of the second survey, 396 individual X-ray sources were detected, of which 164 sources were new detections. When combined with the first survey, this resulted in a total of 560 X-ray sources in the field of M 31. Their (0.1 keV-2.0 keV) fluxes range from 7 x 10<sup>-15</sup> to 7.6 x 10<sup>-12</sup> erg cm<sup>-2</sup> s<sup>-1</sup>, and of these 560 sources, 55 are tentatively identified with foreground stars, 33 with globular clusters, 16 with supernova remnants, and 10 with radio sources and galaxies (including M 32). A comparison with the results of the Einstein M 31 survey reveals 491 newly detected sources, 11 long-term variable sources, and 7 possible transient sources. Comparing the two ROSAT surveys, Supper et al. come up with 34 long-term variable sources and 8 transient candidates. For the M 31 sources, the observed X-ray luminosities range from 4 x 10<sup>35</sup> to 4 x 10<sup>38</sup> erg s<sup>-1</sup>. The total (0.1 keV-2.0 keV) luminosity of M 31 is (3.4 +/- 0.3) x 10<sup>39</sup> erg s<sup>-1</sup>, distributed approximately equally between the bulge and disk. Within the bulge region, the luminosity of a possible diffuse component combined with faint sources below the detection threshold is (2.0 +/- 0.5) x 10<sup>38</sup> erg s<sup>-1</sup>. An explanation in terms of hot gaseous emission leads to a maximum total gas mass of (1.0 +/- 0.3) x 10<sup>6</sup> solar masses. The conversion of PSPC count rates into X-ray fluxes depends on the assumed spectral shape. For M 31-sources, a power law with photon index of -2.0 and an intervening column density pf 9 x 10<sup>20</sup> H atoms cm<sup>-2</sup> may be used, leading to the conversion factor of 1 ct/ksec = 3.00 x 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup> in the 0.1-2.0 keV broad band. For foreground stars, the application of this conversion factor leads to an over-estimate of the fluxes. This online catalog was created by the HEASARC in October 2001 based on machine-readable tables obtained from the ADC/CDS data centers (their catalog J/A+A/373/63, and table table6.dat). This is a service provided by NASA HEASARC .
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