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Paper: The population of supersoft sources in M31
Volume: 157, Annapolis Workshop on Magnetic Cataclysmic Variables
Page: 405
Authors: Kahabka, Peter
Abstract: The population of supersoft sources in M31 is estimated taking a theoretical white dwarf mass distribution into account and under the assumption that the observationally-derived sample is restricted to white dwarf masses above 0.85 Modot. Taking a double exponential scale-height distribution for the gas and the source population into account a total number of 500-17 000 sources is deduced (making use of the predicted population of Yungelson under the Hydrogen-burning shell approximation). The scale height derived for the source population is a factor of 1-10 smaller than the scale height of the gas distribution (of 150-600 pc). The spatial distribution favors a disk (or spiral-arm) dominated, young stellar population with a ratio of 1/(4-7) of bulge/disk systems. This is very similar to what has been found for novae in the Milky Way, but lower than that favored for novae in the M31 galaxy ( 1/2). Supersoft sources and Cepheids both show associations with the M31 spiral arms and may belong to a younger stellar population. A mean space density of (0.1-5) times 10^{-8} pc^{-3} is inferred for the supersoft sources.
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