2014A&A...566A.116R


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.12CET03:08:45

2014A&A...566A.116R - Astronomy and Astrophysics, volume 566A, 116-116 (2014/6-1)

On helium-dominated stellar evolution: the mysterious role of the O(He)-type stars.

REINDL N., RAUCH T., WERNER K., KRUK J.W. and TODT H.

Abstract (from CDS):

About a quarter of all post-asymptotic giant branch (AGB) stars are hydrogen-deficient. Stellar evolutionary models explain the carbon-dominated H-deficient stars by a (very) late thermal pulse scenario where the hydrogen-rich envelope is mixed with the helium-rich intershell layer. Depending on the particular time at which the final flash occurs, the entire hydrogen envelope may be burned. In contrast, helium-dominated post-AGB stars and their evolution are not yet understood. A small group of very hot, helium-dominated stars is formed by O(He)-type stars. A precise analysis of their photospheric abundances will establish constraints to their evolution. We performed a detailed spectral analysis of ultraviolet and optical spectra of four O(He) stars by means of state-of-the-art non-LTE model-atmosphere techniques. We determined effective temperatures, surface gravities, and the abundances of H, He, C, N, O, F, Ne, Si, P, S, Ar, and Fe. By deriving upper limits for the mass-loss rates of the O(He) stars, we found that they do not exhibit enhanced mass-loss. The comparison with evolutionary models shows that the status of the O(He) stars remains uncertain. Their abundances match predictions of a double helium white dwarf (WD) merger scenario, suggesting that they might be the progeny of the compact and of the luminous helium-rich sdO-type stars. The existence of planetary nebulae that do not show helium enrichment around every other O(He) star precludes a merger origin for these stars. These stars must have formed in a different way, for instance via enhanced mass-loss during their post-AGB evolution or a merger within a common-envelope (CE) of a CO-WD and a red giant or AGB star. A helium-dominated stellar evolutionary sequence exists that may be fed by different types of mergers or CE scenarios. It appears likely that all these pass through the O(He) phase just before they become WDs.

Abstract Copyright:

Journal keyword(s): stars: AGB and post-AGB - stars: evolution - stars: fundamental parameters - stars: abundances

CDS comments: Fig.24 HS 1820+72090 misprint for HS 1830+7209

Simbad objects: 34

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Number of rows : 34

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 KPD 0005+5106 WD* 00 08 18.1706793307 +51 23 16.594540226 11.80 13.04 13.32 13.53   DOZ1 113 0
2 ACO 48 ClG 00 31 11 +12 32.6           ~ 9 0
3 PG 0038+199 WD* 00 41 35.3382948562 +20 09 16.906605595   13.82       DO1 36 0
4 PG 0046+078 WD* 00 48 37.8850307259 +08 02 44.856934062   15.59 15.590     DO 18 0
5 EGGR 900 WD* 01 11 06.5712833283 +10 21 38.187085045   14.86       DO 39 1
6 EGGR 901 WD* 01 12 23.0598123991 +11 23 36.100490145   15.15 15.40 15.69   DOZ.7 35 0
7 HS 0111+0012 WD* 01 13 46.7763906618 +00 28 28.645434313   14.59 14.9     DO 29 0
8 BD+37 442 HS* 01 58 33.4340086125 +38 34 23.846108332   9.69 9.92     sdOHe 57 0
9 PG 0237+116 WD* 02 40 06.6412114996 +11 48 28.136992737   15.12       DO 20 0
10 RX J0503.9-2854 WD* 05 03 55.5147387403 -28 54 34.631014015 12.29 13.55 13.58     DO 89 0
11 PN K 1-27 PN 05 57 02.1748480138 -75 40 22.475592752       16.27 16.41 sdOHe 79 0
12 SDSS J075732.18+184329.3 WD* 07 57 32.1843198283 +18 43 29.330396679   18.0   18.9   PG1159/O(He) 7 0
13 CD-45 5058 HS* 09 20 10.1321975829 -45 31 54.939916304 9.81 11.03 11.33 11.62   sdO 47 0
14 BD+37 1977 HS* 09 24 26.3928822549 +36 42 53.293596680   9.86 10.15     sdO 39 0
15 PG 1034+001 WD* 10 37 03.8005751967 -00 08 19.122434186 11.589 12.863 13.228 13.383 13.587 DO 105 0
16 V* DN Leo Pu* 10 38 55.2344094277 +10 03 48.485524647   9.76 9.93     Bp 133 0
17 ESO 320-28 PN 11 52 29.231 -42 17 38.69           ~ 51 0
18 V* GW Vir WD* 12 01 45.9728868858 -03 45 40.627851273   14.87 15.04     DOQZ1 458 0
19 V* DY Cen RC* 13 25 34.0847442636 -54 14 43.129740133     12.00     C-Hd/B5-6Ie 83 0
20 CD-46 8926 HS* 13 53 08.2145759352 -46 43 42.320124869   11.04 11.30     sdO 36 0
21 SDSS J141812.51-024426.8 WD* 14 18 12.5145124008 -02 44 27.002321347           PG1159/O(He) 8 0
22 HS 1522+6615 WD* 15 22 56.6961693247 +66 04 42.031617922   16.4       DO 23 0
23 V* R CrB RC* 15 48 34.4147978750 +28 09 24.298218765 6.44 6.31 5.71 5.26 5.08 G0Iep 755 0
24 HD 144941 pA* 16 09 24.5510961490 -27 13 38.185973432 9.45 10.17 10.02     B8 77 1
25 LSE 259 HS* 16 53 54.5761511888 -56 01 54.752384338     12.54     sdO 30 0
26 SDSS J171916.96+365326.7 WD* 17 19 16.9663647477 +36 53 26.757590743   17.7   18.3   PG1159/O(He) 6 0
27 SDSS J172854.34+361958.6 WD* 17 28 54.3428227102 +36 19 58.616043599   16.8   17.2   PG1159/O(He) 8 0
28 HD 160641 HS* 17 41 51.5794261316 -17 53 48.460430048 9.15 10.01 9.85 10.08 9.59 sdOC9.5II-IIIHe40 113 0
29 IC 4663 PN 17 45 28.6294985056 -44 54 17.982999895           [WN3] 91 0
30 HS 1830+7209 WD* 18 30 04.7128828985 +72 11 35.945507951   16.1   17.1   DO 10 0
31 PN G009.8-07.5 PN 18 36 22.820 -23 55 18.26       13.52 12.44 ~ 86 0
32 CD-51 11879 HS* 19 02 11.7422717452 -51 30 09.556345077   11.44 11.55     sdO 33 0
33 PG 2158+082 HS* 22 01 02.2828954593 +08 30 47.913417950   12.8 13.38 13.49   sdO2VIIIHe40 12 0
34 HS 2209+8229 WD? 22 08 25.8770882750 +82 44 51.412639578   16.0       DO/sdO 12 0

    Equat.    Gal    SGal    Ecl

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2019.11.12-03:08:45

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