2007A&A...462..269S


Query : 2007A&A...462..269S

2007A&A...462..269S - Astronomy and Astrophysics, volume 462, 269-280 (2007/1-4)

Hot subdwarfs from the ESO supernova Ia progenitor survey. II. Atmospheric parameters of subdwarf O stars.

STROEER A., HEBER U., LISKER T., NAPIWOTZKI R., DREIZLER S., CHRISTLIEB N. and REIMERS D.

Abstract (from CDS):

We address the origin and evolutionary status of hot subdwarf stars by studying the optical spectral properties of 58 subdwarf O (sdO) stars. Combining them with the results of our previously studied subdwarf B (sdB) stars, we aim at investigating possible evolutionary links. We analyse high-resolution (R>18000), high-quality optical spectra of sdO stars obtained with the ESO VLT UVES echelle spectrograph in the course of the ESO Supernova Ia Progenitor Survey (SPY). Effective temperatures, surface gravities, and photospheric helium abundances are determined simultaneously by fitting the profiles of hydrogen and helium lines using dedicated synthetic spectra calculated from an extensive grid of NLTE model atmospheres. We find spectroscopic or photometric evidence for cool companions to eight sdO stars, as well as a binary consisting of two sdO stars. A clear correlation between helium abundances and the presence of carbon and/or nitrogen lines is found: below solar helium abundance, no sdO star shows C or N lines. In contrast, C and/or N lines are present in the spectra of all sdO stars with supersolar helium abundance. We thus use the solar helium abundance to divide our sample into helium-deficient and helium-enriched sdO stars. While helium-deficient sdO stars are scattered in a wide range of the Teff-log(g)-diagram, most of the helium-enriched sdO stars cluster in a narrow region at temperatures between 40000 and 50000K and gravities between logg=5.5 and 6.0. An evolutionary link between sdB stars and sdO stars appears plausible only for the helium-deficient sdO stars. They probably have evolved away from the extreme horizontal branch; i.e., they are the likely successors to sdB stars. In contrast, the atmospheric properties of helium-enriched sdO stars cannot be explained with canonical single-star evolutionary models. Alternative scenarios for both single-star (late hot flasher) and binary evolution (white-dwarf merger; post-RGB evolution) fail to reproduce the observed properties of helium-enriched sdO stars in detail. While we regard the post-RGB scenario as inappropriate, the white-dwarf merger and the late hot-flasher scenarios remain viable to explain the origin of helium-enriched sdO stars.

Abstract Copyright:

Journal keyword(s): binaries: spectroscopic - stars: abundances - stars: atmospheres - stars: fundamental parameters - stars: horizontal-branch - stars: subdwarfs

Simbad objects: 56

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Number of rows : 56
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 Ton S 133 HS* 00 01 38.4853059312 -28 27 43.030914948   16.6 16.14     sdO7He2 18 0
2 Ton S 137 HS* 00 04 31.0012800744 -24 26 21.321904200   13.66 13.8     sdO8He4 27 0
3 Ton S 148 HS* 00 18 53.2163245368 -31 56 01.925829492   14.27 14.45     sdBC0.2VIHe37 10 0
4 PG 0026+136 HS* 00 28 52.2594314712 +13 54 46.593864288   15.84 16.00     sdO 13 0
5 JL 199 HS* 00 34 07.7459679312 -55 51 05.933690604   15.5       sdOHe 6 0
6 LB 1568 HS* 00 42 30.9580207368 -48 22 14.699554320   16.07     16.72 sdO 4 0
7 MCT 0111-1526 HS* 01 13 38.2345547736 -15 11 02.274731052   14.68 14.85 15.13   sdO7He3 10 0
8 HE 0155-3710 HS* 01 58 01.4668425840 -36 56 21.345844092   15.08       sdO8He3 5 0
9 Ton S 313 HS* 03 03 43.9021085664 -30 27 47.659887828           sdB 11 0
10 BPS CS 22190-0003 HS* 03 44 58.8250755048 -16 52 42.177140472 13.52 14.63 14.90     sdOHe 10 0
11 HE 0414-5429 HS* 04 15 30.2247283728 -54 21 58.605323616 13.40 14.67 15.12     sdO8VIIHe39 9 0
12 HZ 1 HS* 04 50 13.5220981656 +17 42 06.198493500   12.601 12.661     sdOHe 36 0
13 PG 0914-037 HS* 09 17 15.5883022512 -03 53 56.000023080   14.93       sdOHe 8 1
14 GD 104 HS* 09 47 03.3494055240 -09 19 49.517312124   15.59 15.89 15.71   sdOpec 17 0
15 PG 0956+021 WD* 09 58 50.5157308008 +01 47 24.166179060   16.05   16.1   DA3.0 32 0
16 PG 0958-119 HS* 10 00 42.5868055272 -12 05 59.230105008   13.84 14.05 14.28   sdO8VIIHe39 15 0
17 HE 1008-1757 HS* 10 10 33.4059194640 -18 11 47.615736012   14.89 15.15 15.59   sdO 8 0
18 PG 1047-066 HS* 10 50 28.7935274352 -06 53 25.969327980   14.51 14.77 15.11   sdO 8 0
19 HE 1059-2735 HS* 11 01 24.8687002296 -27 51 41.914393668   15.21 15.56     sdO 9 0
20 PG 1106-097 HS* 11 09 08.1796130592 -09 58 47.589730608   16.9   16.4   sdO 7 0
21 PG 1115-065 HS* 11 18 11.6492036328 -06 47 32.162282988   14.83 15.08 15.59   sdO 11 0
22 PG 1130-063 HS* 11 32 41.5864573608 -06 36 52.766853516   16.2   16.0   sdO 12 0
23 PG 1135-116 HS* 11 38 10.5713473824 -11 51 03.574348560   15.45       sdOHe 11 0
24 EC 11363-1641 HS* 11 38 54.5078119824 -16 58 12.311467320   15.16 15.43     sdOHe 5 0
25 HE 1136-2504 HS* 11 39 10.2231003744 -25 20 55.561030836   13.89 14.10 14.67   sdOHe 9 0
26 HE 1142-2311 HS* 11 44 50.1480166440 -23 28 18.466147488   15.40 15.52 15.66   sdOHe 6 0
27 CD-22 9142 HS* 11 50 38.8492465464 -23 20 34.600310232   11.57 11.79     sdOB 24 0
28 Feige 54 HS* 12 02 40.0889106504 -19 41 07.945079712   14.15 14.45     sdOHe 6 0
29 PG 1203-108 HS* 12 05 56.5574673864 -11 05 28.216976424   15.69       sdOHe 7 0
30 PG 1237-141 HS* 12 39 56.5402601160 -14 24 47.723882508   16.13 16.31     sdO 8 0
31 HE 1238-1745 HS* 12 41 01.1118607776 -18 01 57.242438220   14.36 14.58 15.21   sdOHe 11 0
32 PG 1251+019 HS* 12 54 08.3239424832 +01 43 24.111086088   15.24       sdOHe 18 0
33 HE 1256-2738 HS* 12 59 01.3945837008 -27 54 18.765895284   16.9 16.46 16.2   sdOHe 17 0
34 PG 1258+012 HS* 13 00 59.2051279416 +00 57 11.766735576   16.6   16.7   sdOHe 22 0
35 HE 1310-2733 HS* 13 12 50.5865006472 -27 49 01.842181464   14.24 14.45 14.75   sdOHe 11 0
36 EC 13165-1834 HS* 13 19 16.9516685112 -18 49 51.651262524   16.6 16.29 16.6   sdOHe 6 0
37 HE 1318-2111 HS* 13 21 15.6370363200 -21 27 17.629351236   14.57 14.77     sdO 13 0
38 HE 1349-2320 HS* 13 52 14.8434471264 -23 34 57.581319252   15.26 15.51 15.91   sdO 5 0
39 PG 1355-064 HS* 13 57 54.2609548056 -06 37 31.924474572   13.38 13.68 14.10   sdO2VIIIHe40 12 0
40 HE 1356-1613 HS* 13 59 12.5110775616 -16 28 01.792106796   16.1   16.3 16.79 sdO 5 0
41 PG 1423-013 HS* 14 25 51.2878581720 -01 33 17.248338720   16.7   16.9   sdO 10 0
42 PG 1430-083 HS* 14 33 36.8012804880 -08 28 23.248125984   15.71 16.05     sdOHe 10 1
43 EC 14466-1058 HS* 14 49 24.4156834752 -11 11 18.029512932   15 15.21     sdOHe 5 0
44 PG 1502-103 HS* 15 05 22.6981844280 -10 31 26.007996468   15.56 15.53 15.66   sdB 8 0
45 PG 1511-110 HS* 15 14 16.9962679704 -11 14 12.482699604   14.80 14.97 15.23   sdOHe 9 0
46 PG 1512-035 HS* 15 14 50.0513833920 -03 42 49.896045468   16.16 16.37 16.20   sdOB 9 0
47 PG 1513-045 HS* 15 16 19.1197607616 -04 43 57.452560464   15.57 15.73 16.09   sdO 5 0
48 PG 1518-098 HS* 15 20 59.2889341440 -09 58 56.435730708   13.48 13.67 14.03   sdOC2VIeHe40 9 0
49 PG 1632+223 HS* 16 34 16.0910673336 +22 11 41.100861624   15.23 15.52 15.95   sdOHe 11 1
50 HD 188112 HS* 19 54 31.4191828536 -28 20 20.679710640   10.01 10.22     sdB 88 0
51 BPS CS 22955-0024 HS* 20 23 50.2879686360 -25 08 29.033493540 14.29 15.50 15.5     sdOHe 9 0
52 HE 2203-2210 HS* 22 06 29.3837853216 -21 55 59.664956520   15.04       sdOHe 5 0
53 PG 2204+070 WD* 22 07 16.0954367568 +07 18 37.230359652   15.4   15.1   DA2.0 16 0
54 PHL 231 HS* 22 21 12.9983909568 -20 11 17.209935528   16.28 16.8     sdOHe 7 0
55 PG 2258+155 HS* 23 00 57.7424130816 +15 48 40.451383800   15.03   15.6   sdB0.2VIIHe39 17 0
56 HE 2347-4130 HS* 23 50 19.7137825608 -41 14 01.174503372   15.16       sdO8VIIHe39 7 0

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2022.05.21-15:37:35

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