2003A&A...397.1043K


Query : 2003A&A...397.1043K

2003A&A...397.1043K - Astronomy and Astrophysics, volume 397, 1043-1055 (2003/1-3)

A new look at the pulsating DB white dwarf GD 358: Line-of-sight velocity measurements and constraints on model atmospheres.

KOTAK R., VAN KERKWIJK M.H., CLEMENS J.C. and KOESTER D.

Abstract (from CDS):

We report on our findings of the bright, pulsating, helium atmosphere white dwarf GD 358, based on time-resolved optical spectrophotometry. We identify 5 real pulsation modes and at least 6 combination modes at frequencies consistent with those found in previous observations. The measured Doppler shifts from our spectra show variations with amplitudes of up to 5.5km/s at the frequencies inferred from the flux variations. We conclude that these are variations in the line-of-sight velocities associated with the pulsational motion. We use the observed flux and velocity amplitudes and phases to test theoretical predictions within the convective driving framework, and compare these with similar observations of the hydrogen atmosphere white dwarf pulsators (DAVs). The wavelength dependence of the fractional pulsation amplitudes (chromatic amplitudes) allows us to conclude that all five real modes share the same spherical degree, most likely, l=1. This is consistent with previous identifications based solely on photometry. We find that a high signal-to-noise mean spectrum on its own is not enough to determine the atmospheric parameters and that there are small but significant discrepancies between the observations and model atmospheres. The source of these remains to be identified. While we infer Teff=24kK and logg∼8.0 from the mean spectrum, the chromatic amplitudes, which are a measure of the derivative of the flux with respect to the temperature, unambiguously favour a higher effective temperature, 27kK, which is more in line with independent determinations from ultra-violet spectra.

Abstract Copyright:

Journal keyword(s): stars: white dwarfs - stars: oscillations - stars: atmospheres, convection - stars: individual: GD 358

Simbad objects: 8

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Number of rows : 8
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 HL Tau 76 WD* 04 18 56.6378191680 +27 17 48.314513652   15.40       DA4.3 133 0
2 BD+52 913 WD* 05 05 30.6180977592 +52 49 51.919301604 10.25 11.44 11.69 11.93 12.108 DA.8 1040 0
3 HS 0507+0434B WD* 05 10 13.5215260416 +04 38 55.135549140   15.52 15.31 15.63   DA2.3 58 0
4 GD 358 WD* 16 47 18.3925183824 +32 28 32.862804384 12.511 13.530 13.653 13.752 13.852 DB2 334 0
5 V* DN Dra WD* 16 48 25.6318375106 +59 03 22.658985521   12.34 12.17 12.44   DA4.0 205 0
6 V* PY Vul WD* 19 37 13.7502269447 +27 43 18.733503670   13.14   12.7   DA4.0 121 0
7 HD 340611 WD* 20 34 21.8847019255 +25 03 49.750446346 10.687 11.471 11.546 11.648 11.728 DA2.4 298 0
8 V* ZZ Psc WD* 23 28 47.6365087803 +05 14 54.235051503   13.17   13.0   DA4.1 462 0

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2022.08.16-05:45:07

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