1995A&A...300..481B


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.18CEST04:07:30

1995A&A...300..481B - Astronomy and Astrophysics, volume 300, 481-492 (1995/8-2)

Metal abundances in subdwarf O stars.

BAUER F. and HUSFELD D.

Abstract (from CDS):

We describe a non-LTE analysis of seven subdwarf O stars and four central stars of planetary nebulae. The analysis yields metal abundances (or upper limits to these) of C, N, O, Mg, Al, and Si for most of these stars. Also effective temperature, surface gravity and helium abundance were determined for those programme stars for which no reliable estimates of these parameters were available. The derived abundance patterns prove to be disparate. We also compare the sdO stars in our sample with other sdO analyses (18 object in total) and find that this stellar class is not homogeneous with respect to metal abundances. A tentative subclassification according to helium content and luminosity-to-mass ratio indicates that the compact, high-gravity sdO stars have similar metal abundances with a strong signature of hydrogen burning in the CNO cycle. They only differ in the amounts of helium and carbon present in the photosphere, probably caused by varying efficiencies of mixing or surface erosion. Luminous sdOs, on the other hand, show markedly different metallicities, suggesting different origins. The star CPD-31 1701 is identified as a peculiar object. As compared with other O subdwarfs with nearly identical parameters, its He II line profiles appear shallow and rounded, lacking a well defined core. They can also not be fitted by theoretical profiles. No explanation for this discrepancy could be found yet. Our analysis yields microturbulence velocities in the range 0-10km/s for all stars with a sufficient number of metal lines. No indication was found for higher values like the 20km/s reported by Hubeny et al. (1991) for the sdO star BD+75 325.

Abstract Copyright:

Journal keyword(s): subdwarfs - stars: abundances - stars: atmospheres - stars: early type

CDS comments: ROB 162 = NGC 6397 162

Simbad objects: 18

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Number of rows : 18

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 PG 0057+155 HS* 00 59 56.6671977894 +15 44 13.737246975   12.02 12.32     sdB0.2VIIIpHe8 117 1
2 BD+37 442 HS* 01 58 33.4340086125 +38 34 23.846108332   9.69 9.92     sdOHe 61 0
3 NGC 1535 PN 04 14 15.7689951134 -12 44 21.934169738   12.01 12.82     sdO3: 504 0
4 HD 49798 HXB 06 48 04.7000758397 -44 18 58.432035331 6.758 8.017 8.287 8.391 8.543 sdO6 288 0
5 NGC 2392 PN 07 29 10.7669120392 +20 54 42.478515772     9.68     O6f 702 1
6 CPD-31 1701 HS* 07 36 30.1947256655 -32 12 43.685247834 9 10.26 10.48 10.81   sdO8p 61 0
7 BD+75 325 HS* 08 10 49.4901623070 +74 57 57.936226530 8.002 9.23 9.50 9.698 9.884 sdO5 236 0
8 CD-45 5058 HS* 09 20 10.1321975829 -45 31 54.939916304 9.81 11.03 11.33 11.62   sdO 50 0
9 Feige 46 HS* 11 37 26.3700093153 +14 10 14.103354248   12.94 13.24     sdO 41 0
10 BD+18 2647 HS* 12 41 51.7901702595 +17 31 19.750592670 10.261 11.70 11.63 11.969 12.159 sdOpec 166 1
11 CD-46 8926 HS* 13 53 08.2145759352 -46 43 42.320124869   11.04 11.30     sdO 38 0
12 HD 127493 HS* 14 32 21.4928221685 -22 39 25.645935056 8.64 9.74 10.08     sdOHe 88 0
13 LS IV -12 1 HS* 16 23 43.9894821460 -12 12 33.641936636 10.06 11.14 11.17     sdO 31 0
14 LSE 259 HS* 16 53 54.5761511888 -56 01 54.752384338     12.54     sdO 31 0
15 NGC 6397 162 HS* 17 40 38.4614296064 -53 38 31.346327354   13.06 13.23     sdOp 40 1
16 CD-51 11879 HS* 19 02 11.7422717452 -51 30 09.556345077   11.44 11.55     sdO 35 0
17 NGC 7293 PN 22 29 38.5453078023 -20 50 13.746093105 11.894 13.158 13.524 13.689 13.898 DAO.5 910 0
18 CD-30 19716 HS* 23 52 36.0932797836 -30 10 09.115787067   11.97 12.86     sdO6He2 27 0

    Equat.    Gal    SGal    Ecl

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