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Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B : New constraints on mode identification and pulsation properties

Kotak, Rubina LU ; van Kerkwijk, M. H. and Clemens, J. C. (2002) In Astronomy & Astrophysics 388(1). p.219-234
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ZZ Psc -- white dwarfs -- oscillations -- convection, stars: individual: HS 0507+0434
in
Astronomy & Astrophysics
volume
388
issue
1
pages
219 - 234
publisher
EDP Sciences
external identifiers
  • wos:000175901700025
  • scopus:0036607973
ISSN
0004-6361
DOI
10.1051/0004-6361:20020474
language
English
LU publication?
yes
id
24991385-f0dc-492c-9b40-4309a8c9ed40 (old id 118553)
date added to LUP
2007-07-13 13:44:49
date last changed
2017-01-01 07:14:24
@article{24991385-f0dc-492c-9b40-4309a8c9ed40,
  abstract     = {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.},
  author       = {Kotak, Rubina and van Kerkwijk, M. H. and Clemens, J. C.},
  issn         = {0004-6361},
  keyword      = {ZZ Psc -- white dwarfs -- oscillations -- convection,stars: individual: HS 0507+0434},
  language     = {eng},
  number       = {1},
  pages        = {219--234},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B : New constraints on mode identification and pulsation properties},
  url          = {http://dx.doi.org/10.1051/0004-6361:20020474},
  volume       = {388},
  year         = {2002},
}