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 sur vey of M 31 performed in summer 1992. We compare our results with those of the first survey, already published in Supper et al. (1997). Within the sim ilar to 10.7deg(2) field of view, 396 individual X-ray sources are detected in the second survey data, of which 164 are new detections. When combined with the first survey, this result in a total of 560 X-ray sources in the f ield of M 31. Their (0.1 keV-2.0 keV) fluxes range from 7 x 10(-15) erg cm( -2) s(-1) to 7.6 x 10(-12) erg cm(-2) s(-1), and of these 560 sources, 55 a re tentatively identified with foreground stars, 33 with globular clusters, 16 with supernova remnants, and 10 with radio sources and galaxies (includ ing M 32). A comparison with the results of the Einstein M 31 survey reveal s 491 newly detected sources, 11 long term variable sources, and 7 possible transient sources. Comparing the two ROSAT surveys, we come up with 34 lon g term variable sources and 8 transient candidates. For the M 31 sources, t he observed luminosities range from 4 x 10(35) erg s(-1) to 4 x 10(38) erg s(-1). The total (0.1 keV-2.0 keV) luminosity of M 31 is (3.4 +/-0.3) x 10( 39) erg s(-1), distributed approximately equally between the bulge and disk . Within the bulge region, the luminosity of a possible diffuse component c ombined with faint sources below the detection threshold is (2.0 +/-0.5) x 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) x 10(6) M-circle dot.