1999A&A...344..459K

Query : 1999A&A...344..459K

1999A&A...344..459K - Astronomy and Astrophysics, volume 344, 459-471 (1999/4-2)

The M 31 population of supersoft sources.

KAHABKA P.

Abstract (from CDS):

The 1991 ROSAT PSPC M 31 X-ray point source catalog has been screened in order to set up a sample of candidate supersoft sources in this galaxy, additional to the 16 supersoft sources already known in M 31 (Supper et al., 1997A&A...317..328S). Selection criteria used were based on hardness ratios (``X-ray colors''), as developed in an earlier paper (Kahabka, 1998A&A...332..189K). An additional criterion to be fulfilled was that the observed count rate is in agreement with the expected steady-state luminosity for a source with these hardness ratios. This condition constrained mainly the hydrogen absorbing column towards the source. 26 candidates not correlating with foreground stars and M 31 supernova remnants have been found to fulfil one of the selection criteria. They can be considered to be candidate supersoft sources in M 31. This comprises 6% of all point sources in this galaxy. For these candidates absorbing hydrogen column densities, effective temperatures and white dwarf masses (assuming the sources are on the stability line of surface nuclear burning) are derived. An observed white dwarf mass distribution is derived which indicates that the masses are constrained to M>0.90M☉. The entire population of supersoft sources in M 31 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 0.90M☉. Taking into account that the gas and the source population have different scale heights a total number of at least 200-500 and at most 6,000-15,000 sources is deduced (depending on the used galaxy NH model), making use of the population synthesis calculation of Yungelson et al. (1996ApJ...466..890Y). The spatial distribution favors a disk (or spiral-arm) dominated young stellar population with a ratio of 1/(4-7) of bulge/disk systems, very similar to what has been found for novae in the Milky Way but lower than favored for novae in M 31 (∼1/2). Supersoft sources and Cepheids both show association with the M 31 spiral arms and may belong to a younger stellar population. A mean space density of ~(0.1-5)x10–8pc–3 is inferred for the supersoft sources. Assuming that all supersoft sources with masses in excess of 0.5M☉ are progenitors of supernovae of type Ia, a SN Ia rate of (0.8-7)x10–3yr–1 is derived for M 31 based on these progenitors. Supersoft sources might be able to account for 20-100% of the total SN Ia rate in a galaxy like M 31.

Abstract Copyright: ∼

Journal keyword(s): stars: evolution - stars: white dwarfs - galaxies: individual: M 31 - X-rays: stars

Nomenclature: Table 1: [K99] SWa (Nos SWa-SWo, SWt) N=16, [K99] CNN (Nos C17-C42).

CDS comments: RX J0043.9+5148 misprint for RX J0043.9+4151.

Simbad objects: 53

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Number of rows : 53
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 V* QR And CV* 00 19 49.9252996176 +21 56 52.169584416   12.38 12.73 11.86   Ss 132 0
2 RX J003725.3+401516 X 00 37 25.3 +40 15 16           ~ 10 0
3 RX J0038.5+4014 X 00 38 32.1 +40 14 39           ~ 11 0
4 RX J0038.6+4019 X 00 38 40.55 +40 19 56.4           ~ 12 0
5 TYC 2788-930-1 * 00 39 24.7853118624 +40 50 27.616716528   11.676 10.986 10.910   ~ 6 0
6 RX J003938.5+405409 X 00 39 38.5 +40 54 09           ~ 10 0
7 GPM 9.931229+40.661821 * 00 39 43.5134841600 +40 39 42.594816672   13.64 12.918   12.28 G0 10 0
8 RX J0039.7+4030 SNR 00 39 45.43 +40 29 49.5           ~ 8 0
9 RX J004001.6+410051 X 00 40 01.6 +41 00 51           ~ 5 0
10 RX J0040.1+4021 X 00 40 06.6 +40 21 52           ~ 4 0
11 RX J0040.4+4009 X 00 40 26.3 +40 09 01           ~ 11 0
12 [K99] C20 * 00 40 30.5353513104 +40 34 30.397537092   16.71 16.171 15.80 15.498 ~ 4 0
13 RX J004043.2+401518 X 00 40 43.2 +40 15 18           ~ 11 0
14 RX J004130.2+404004 X 00 41 30.2 +40 40 04           ~ 11 0
15 RX J004149.9+405921 X 00 41 49.9 +40 59 21           ~ 11 0
16 2MASS J00415133+4015123 * 00 41 51.3372778824 +40 15 12.344812632           M5 7 0
17 2MASS J00421645+4048113 SR? 00 42 16.4731484184 +40 48 11.654052444           ~ 9 0
18 RX J004227.6+404432 X 00 42 27.6 +40 44 32           ~ 11 0
19 RX J0042.6+4159 X 00 42 39.4 +41 59 52           ~ 5 0
20 RX J0042.6+4043 X 00 42 39.82 +40 43 18.8           ~ 6 0
21 V* S And No* 00 42 43.12368 +41 16 03.2124           ~ 183 2
22 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12635 1
23 RX J004253.0+411533 X 00 42 52.528 +41 15 40.20           ~ 29 0
24 RX J0042.9+4059 SNR 00 42 55.6 +40 59 39           ~ 6 0
25 RX J004318.6+412024 CV* 00 43 18.851 +41 20 18.52           ~ 24 0
26 BA 1-23 SNR 00 43 27.871 +41 18 29.83           ~ 35 0
27 RX J004335.9+420730 X 00 43 35.9 +42 07 30           ~ 11 0
28 BA 1-55 PN 00 43 39.20 +41 26 52.9     20.35     ~ 34 1
29 RX J0043.7+4127 X 00 43 45.67 +41 27 08.5           ~ 9 0
30 RX J004354.6+415148 X 00 43 54.6 +41 51 48           ~ 5 0
31 RX J004404.8+411820 No* 00 44 04.71 +41 18 21.7           ~ 18 0
32 RX J004412.2+402647 X 00 44 15.3 +40 26 50           ~ 6 0
33 TYC 2805-248-1 * 00 44 23.9229797976 +42 00 09.621420480   11.85 11.14     G0 9 0
34 BA 1-160 SNR 00 45 14.00 +41 36 14.1     21.42     ~ 31 0
35 RX J0045.4+4154 No* 00 45 28.80 +41 54 10.1           ~ 230 1
36 RX J004529.8+421908 X 00 45 29.8 +42 19 08           ~ 8 0
37 RX J0045.5+4206 X 00 45 31.8 +42 07 06           ~ 12 0
38 RX J0046.1+4136 X 00 46 10.1 +41 36 26           ~ 6 0
39 RX J0046.2+4144 X 00 46 15.6 +41 44 36           ~ 11 0
40 RX J004617.8+413848 X 00 46 17.8 +41 38 48           ~ 11 0
41 RX J0046.3+4238 X 00 46 18.2 +42 38 33           ~ 5 0
42 HD 4444 ** 00 47 03.23622 +41 57 53.4071   9.36 9.02     F 20 0
43 RX J0047.0+4201 * 00 47 04.3882075128 +42 01 54.654735756   17.89 17.253   16.592 ~ 4 0
44 RX J0047.6+4132 X 00 47 36.0 +41 32 08           ~ 7 0
45 RX J0047.6+4205 X 00 47 38.5 +42 05 07           ~ 11 0
46 SV* HV 5682 XB* 05 13 50.7836696744 -69 51 47.483136927     16.566 16.606 16.62 ~ 314 0
47 2E 1550 XB* 05 43 34.1600044704 -68 22 22.191505716   15.9   17.2 16.54 ~ 324 0
48 OGLE LMC-SC20 113500 EB* 05 46 46.54 -71 08 53.9     19.163   18.886 ~ 255 0
49 V* T Pyx CV* 09 04 41.5061511720 -32 22 47.502932700           ~ 440 0
50 RX J0925.7-4758 XB* 09 25 46.0017018216 -47 58 17.340963384   19.2       ~ 89 0
51 V* WX Cen WR* 13 12 52.3764011184 -63 23 45.851196156   13.80 13.40     WN3h+WC4 50 0
52 V* V Sge CV* 20 20 14.6911060272 +21 06 10.437106644   11.27 11.22 11.54   Be 214 0
53 [K99] SWt X ~ ~           ~ 1 0

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