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


C.D.S. - SIMBAD4 rel 1.7 - 2020.12.03CET19:35:38

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 - 2021
#notes
1 Ton S 133 HS* 00 01 38.4850507067 -28 27 43.033531913   16.6 16.14     sdO7He2 15 0
2 Ton S 137 HS* 00 04 31.0015375844 -24 26 21.321318009   13.66 13.8     sdO8He4 26 0
3 Ton S 148 HS* 00 18 53.2164656604 -31 56 01.922165697   14.27 14.45     sdO7He3 8 0
4 PG 0026+136 HS* 00 28 52.2592377027 +13 54 46.594975507   15.84 16.00     sdO 12 0
5 JL 199 HS* 00 34 07.7457339246 -55 51 05.933440207   15.5       sdOHe 5 0
6 LB 1568 HS* 00 42 30.9580865796 -48 22 14.701138855   16.07     16.72 sdO 3 0
7 MCT 0111-1526 HS* 01 13 38.2345339917 -15 11 02.275133560   14.68 14.85 15.13   sdO7He3 9 0
8 HE 0155-3710 HS* 01 58 01.4668536999 -36 56 21.347580435   15.08       sdO8He3 4 0
9 Ton S 313 HS* 03 03 43.9022438235 -30 27 47.663892176           sdB 10 0
10 BPS CS 22190-0003 HS* 03 44 58.8251239376 -16 52 42.179845976 13.52 14.63 14.90     sdOHe 9 0
11 HE 0414-5429 HS* 04 15 30.2250172554 -54 21 58.605612312 13.40 14.67 15.12     sdOHe 7 0
12 HZ 1 HS* 04 50 13.5217785460 +17 42 06.198260640   12.601 12.661     sdOHe 32 0
13 PG 0914-037 HS* 09 17 15.5886026464 -03 53 56.000972098   14.93       sdOHe 7 1
14 GD 104 HS* 09 47 03.3494077950 -09 19 49.517356418   15.59 15.89 15.71   sdOpec 16 0
15 PG 0956+021 WD* 09 58 50.5159748587 +01 47 24.166427820   16.05   16.1   DA3.0 31 0
16 PG 0958-119 HS* 10 00 42.5869028362 -12 05 59.231088457   13.84 14.05 14.28   sdOHe 13 0
17 HE 1008-1757 HS* 10 10 33.4058206779 -18 11 47.616227317   14.89 15.15 15.59   sdO 6 0
18 PG 1047-066 HS* 10 50 28.7933072279 -06 53 25.968650715   14.51 14.77 15.11   sdO 7 0
19 HE 1059-2735 HS* 11 01 24.8685849184 -27 51 41.914369709   15.21 15.56     sdO 8 0
20 PG 1106-097 HS* 11 09 08.1796165749 -09 58 47.588183857   16.9   16.4   sdO 5 0
21 PG 1115-065 HS* 11 18 11.6489570021 -06 47 32.162359362   14.83 15.08 15.59   sdO 10 0
22 PG 1130-063 HS* 11 32 41.5865487797 -06 36 52.766442878   16.2   16.0   sdO 10 0
23 PG 1135-116 HS* 11 38 10.5711762877 -11 51 03.572972694   15.45       sdOHe 10 0
24 EC 11363-1641 HS* 11 38 54.5078710008 -16 58 12.313339208   15.16 15.43     sdOHe 4 0
25 HE 1136-2504 HS* 11 39 10.2231069120 -25 20 55.562985112   13.89 14.10 14.67   sdOHe 7 0
26 HE 1142-2311 HS* 11 44 50.1476455560 -23 28 18.464669924   15.40 15.52 15.66   sdOHe 5 0
27 CD-22 9142 HS* 11 50 38.8491644822 -23 20 34.598440877   11.57 11.79     sdOB 22 0
28 Feige 54 HS* 12 02 40.0887065351 -19 41 07.944621226   14.15 14.45     sdOHe 5 0
29 PG 1203-108 HS* 12 05 56.5570856323 -11 05 28.214470946   15.69       sdOHe 6 0
30 PG 1237-141 HS* 12 39 56.5407708748 -14 24 47.727838930   16.13 16.31     sdO 7 0
31 HE 1238-1745 HS* 12 41 01.1117028566 -18 01 57.242824893   14.36 14.58 15.21   sdOHe 9 0
32 PG 1251+019 HS* 12 54 08.3240489960 +01 43 24.112076624   15.24       sdOHe 16 0
33 HE 1256-2738 HS* 12 59 01.3945642122 -27 54 18.770482218   16.9 16.46 16.2   sdOHe 13 0
34 PG 1258+012 HS* 13 00 59.2055058036 +00 57 11.770689604   16.6   16.7   sdOHe 20 0
35 HE 1310-2733 HS* 13 12 50.5863267783 -27 49 01.842815976   14.24 14.45 14.75   sdOHe 9 0
36 EC 13165-1834 HS* 13 19 16.9514481013 -18 49 51.653738249   16.6 16.29 16.6   sdOHe 5 0
37 HE 1318-2111 HS* 13 21 15.6370872757 -21 27 17.630329433   14.57 14.77     sdO 10 0
38 HE 1349-2320 HS* 13 52 14.8436545703 -23 34 57.582123691   15.26 15.51 15.91   sdO 4 0
39 PG 1355-064 HS* 13 57 54.2609296473 -06 37 31.923502914   13.38 13.68 14.10   sdO2VIIIHe40 10 0
40 HE 1356-1613 HS* 13 59 12.5114211880 -16 28 01.804527556   16.1   16.3 16.79 sdO 3 0
41 PG 1423-013 HS* 14 25 51.2876806081 -01 33 17.252813448   16.7   16.9   sdO 9 0
42 PG 1430-083 HS* 14 33 36.8012736777 -08 28 23.251257633   15.71 16.05     sdOHe 9 1
43 EC 14466-1058 HS* 14 49 24.4154494458 -11 11 18.027279145   15 15.21     sdOHe 4 0
44 PG 1502-103 HS* 15 05 22.6986648981 -10 31 26.014358668   15.56 15.53 15.66   sdB 7 0
45 PG 1511-110 HS* 15 14 16.9965600829 -11 14 12.484653526   14.80 14.97 15.23   sdOHe 8 0
46 PG 1512-035 HS* 15 14 50.0514999976 -03 42 49.898227469   16.16 16.37 16.20   sdOB 7 0
47 PG 1513-045 HS* 15 16 19.1204614415 -04 43 57.460947003   15.57 15.73 16.09   sdO 4 0
48 PG 1518-098 HS* 15 20 59.2888567267 -09 58 56.436531561   13.48 13.67 14.03   sdOC2VIeHe40 8 0
49 PG 1632+223 HS* 16 34 16.0910931429 +22 11 41.100693384   15.23 15.52 15.95   sdOHe 10 1
50 HD 188112 HS* 19 54 31.4192112333 -28 20 20.679022097   10.01 10.22     sdB 79 0
51 BPS CS 22955-0024 HS* 20 23 50.2880306564 -25 08 29.033198811 14.29 15.50 15.5     sdOHe 8 0
52 HE 2203-2210 HS* 22 06 29.3835326286 -21 55 59.661557438   15.04       sdOHe 4 0
53 PG 2204+070 WD* 22 07 16.0954050218 +07 18 37.227410972   15.4   15.1   DA2.0 15 0
54 PHL 231 HS* 22 21 12.9985454693 -20 11 17.206585485   16.28 16.8     sdOHe 6 0
55 PG 2258+155 HS* 23 00 57.7425880098 +15 48 40.452515107   15.03   15.6   sdB0.2VIIHe39 16 0
56 HE 2347-4130 HS* 23 50 19.7134941783 -41 14 01.174215112   15.16       sdOHe 5 0

    Equat.    Gal    SGal    Ecl

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2020.12.03-19:35:38

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