| Issue |
A&A
Volume 388, Number 1, June II 2002
|
|
|---|---|---|
| Page(s) | 219 - 234 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361:20020474 | |
| Published online | 28 May 2002 | |
Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B*
New constraints on mode identification and pulsation properties
1
Lund Observatory, Box 43, 22100 Lund, Sweden
2
Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands e-mail: M.H.vanKerkwijk@astro.uu.nl
3
Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA e-mail: clemens@physics.unc.edu
Corresponding author: R. Kotak, rubina@astro.lu.se
Received:
11
September
2001
Accepted:
25
March
2002
We present a detailed analysis of time-resolved optical spectra
of the ZZ Ceti white dwarf, HS 0507+0434B.
Using the wavelength dependence of observed mode amplitudes, we
deduce the spherical degree, 
, of the modes, most of which
have 
. The presence of a large number of combination
frequencies (linear sums or differences of the real modes) enabled
us not only to test theoretical predictions but also to indirectly
infer spherical and azimuthal degrees of real modes that had no
observed splittings. In addition to the above, we measure line-of-sight
velocities from our spectra. We find only marginal evidence for
periodic modulation associated with the pulsation modes: at the frequency
of the strongest mode in the lightcurve, we measure an amplitude of
km s-1, which has a probability of 2% of being due
to chance; for the other modes, we find lower values. Our velocity amplitudes
and upper limits are smaller by a factor of two compared to the amplitudes
found in ZZ Psc. We find that this is consistent with expectations based
on the position of HS 0507+0434B in the instability strip.
Combining all the available information from data such as ours is a first
step towards constraining atmospheric properties in a convectionally
unstable environment from an observational perspective.
Key words: stars: individual: HS 0507+0434, ZZ Psc / white dwarfs / oscillations / convection
The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.
© ESO, 2002
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