Results from deep ROSAT PSPC surveys of M31.
Abstract
ROSAT has performed two pointed PSPC surveys of M31 in 1991 and 1992, adding up to ≡400 ks of total exposure time. The limited sensitivity of both surveys is of the order of ≡1035erg/s leading to the discovery of 560 sources in the field of view. A comparison with the 108 X-ray sources detected with the Einstein observatory confirmed 90% of the latter. Of the ROSAT-sources 121 could be identified by correlations with optical and radio catalogs. Spectral and timing investigations were performed showing a similar variety of source types like in the Milky Way. X-ray sources associated with globular clusters show a comparable luminosity distribution like the one seen in our Galaxy when using the Kaplan-Meyer estimator to obtain a nonparametric estimate of the cumulative distribution function. Statistical methods allow statements about the nonidentified part of X-ray sources in M31. A detailed comparison between both ROSAT-surveys uncovered possible transient candidates. Considerations of the X-ray surface luminosity and the absorption properties of M31 indicate diffuse emission and absorption in the ROSAT energy band.
- Publication:
-
Roentgenstrahlung from the Universe
- Pub Date:
- February 1996
- Bibcode:
- 1996rftu.proc..361S
- Keywords:
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- Andromeda Galaxy: X-Ray Surveys;
- Andromeda Galaxy: X-Ray Sources