The second ROSAT PSPC survey of M 31 and the complete ROSAT PSPC source list

This paper reports the results of the analysis of the second ROSAT PSPC survey of M 31 performed in summer 1992. We compare our results with those of the rst survey, already published in Supper et al. (1997). Within the10: 7d eg 2 eld of view, 396 individual X-ray sources are detected in the second survey data, of which 164 are new detections. When combined with the rst survey, this result in a total of 560 X-ray sources in the eld of M 31. Their (0.1 keV{2.0 keV) fluxes range from 7 10 15 erg cm 2 s 1 to 7:6 10 12 erg cm 2 s 1 , and of these 560 sources, 55 are tentatively identied 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, we come up with 34 long term variable sources and 8 transient candidates. For the M 31 sources, the observed luminosities range from 4 10 35 erg s 1 to 4 10 38 erg s 1 . The total (0.1 keV{2.0 keV) luminosity of M 31 is (3:4 0:3) 10 39 erg s 1 , distributed approximately equally between the bulge and disk. Within the bulge region, the luminosity of a possible diuse component combined with faint sources below the detection threshold is (2:0 0:5) 10 38 erg s 1 . An explanation in terms of hot gaseous emission leads to a maximum total gas mass of (1:0 0:3) 10 6 M.