2014A&A...568A.118K


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.22CEST11:58:49

2014A&A...568A.118K - Astronomy and Astrophysics, volume 568A, 118-118 (2014/8-1)

Atmospheric parameters and carbon abundance for hot DB white dwarfs.

KOESTER D., PROVENCAL J. and GAENSICKE B.T.

Abstract (from CDS):

Atmospheric parameters for hot DB (helium atmosphere) white dwarfs near effective temperatures of 25000K are extremely difficult to determine from optical spectroscopy. The neutral He lines reach a maximum in this range and change very little with effective temperature and surface gravity. Moreover, an often unknown amount of hydrogen contamination can change the resulting parameters significantly. This is particularly unfortunate because this is the range of variable DBV or V777 Her stars. Accurate atmospheric parameters are needed to help or confirm the asteroseismic analysis of these objects. Another important aspect is the new class of white dwarfs - the hot DQ - whose spectra are dominated by carbon lines. The analysis shows that their atmospheres are pure carbon. The origin of these stars is not yet understood, but they may have an evolutionary link with the hotter DBs, as studied here. Our aim is to determine accurate atmospheric parameters and element abundances and study the implications for the evolution of white dwarfs of spectral classes DB and hot DQ. High-resolution UV spectra of five DBs were studied with model atmospheres. We determined stellar parameters and abundances or upper limits of C and Si. These objects were compared with cooler DBs below 20000K. We find photospheric C and no other heavy elements - with extremely high limits on the C/Si ratio - in two of the five hot DBs. We compare various explanations for this unusual composition that have been proposed in the literature: accretion of interstellar or circumstellar matter, radiative levitation, carbon dredge-up from the deeper interior below the helium layer, and a residual stellar wind. None of these explanations is completely satisfactory, and the problem of the origin of the hot DQ remains an open question.

Abstract Copyright:

Journal keyword(s): white dwarfs - convection - stars: abundances

Simbad objects: 20

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Number of rows : 20

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 EGGR 513 WD* 01 03 24.5382564455 -06 32 10.897473656   13.92 13.91     DB3 39 0
2 EGGR 409 WD* 01 14 37.6542285316 +10 41 04.756788413   15.27 15.41 15.69   DB2.5 57 0
3 G 35-26 WD* 02 05 49.6964349614 +20 57 07.959912353   17.1   17.4   DAQ3 43 0
4 WG 7 WD* 03 09 47.9177903982 -56 23 49.413047243   13.99 14.14 14.42   DB 42 0
5 HE 0420-4748 WD* 04 22 11.3564971436 -47 41 42.015673094 14.08 15.10 15.24     DB 11 0
6 GD 61 WD* 04 38 39.3737549429 +41 09 32.348595654 13.801 14.767 14.879 14.932 14.970 DBAZ3 73 0
7 V* HR Cam WD* 07 17 09.7856980174 +74 00 40.533860068   14.91 14.97     DA2.6 63 0
8 Ton 10 WD* 08 43 59.3692943703 +26 02 56.591825267   14.68 14.78     DB3 31 0
9 V* DT Leo WD* 11 18 22.6933636487 +15 33 34.537492711   16.90   16.88   DB2 46 0
10 PG 1501+664 WD* 15 02 09.6296551839 +66 12 19.146114550   16.07 16.37     DZQ1 148 0
11 GD 190 WD* 15 44 19.4544619130 +18 06 43.778576704 13.537 14.556 14.677 14.767 14.849 DB2 76 0
12 KUV 15571+1913 WD* 15 59 21.0798596049 +19 04 08.303154260   15.5 15.4     DB 17 0
13 GD 358 WD* 16 47 18.3926893312 +32 28 32.865420612 12.511 13.530 13.653 13.752 13.852 DB2 312 0
14 PG 1654+160 WD* 16 56 57.6525864228 +15 56 25.377328132   16.2   15.4   DB2 48 0
15 GD 524 WD* 17 28 56.2199462336 +55 58 22.632470319   16.19   15.89   DBQ4 43 0
16 GD 378 WD* 18 23 37.0115357579 +41 04 02.105626146 13.246 14.208 14.288 14.324 14.379 DBAZ4 59 0
17 KIC 8626021 WD* 19 29 04.6789361529 +44 47 09.026641841   18.3   18.5   DB 21 0
18 L 1573-31 WD* 19 42 13.0000598717 +37 31 56.598511711   14.42   14.5   DB1 42 1
19 V* QU Tel WD* 20 09 40.1876131002 -52 25 15.865114037 14.51 15.25 15.03     DB2 48 0
20 LAWD 89 WD* 21 47 37.288800 -07 44 12.37632 13.752 14.77 14.83 14.96 14.889 DB0 63 0

    Equat.    Gal    SGal    Ecl

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2019.10.22-11:58:49

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