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

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, l, of the modes, most of which have l=1. 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 2.6+/-1.0 km/s, 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.

16 pages, 12 figs.; accepted for publication in A&A

References in corpus (1)

• Nonlinear effects in time-resolved spectra of DAVs

Cited by in corpus (16)

• Evolutionary and pulsational properties of white dwarf stars
• Ensemble Characteristics of the ZZ Ceti stars
• A New Technique for Probing Convection in Pulsating White Dwarf Stars
• Asteroseismology of the ZZ Ceti star HS 0507+0434B
• New evolutionary models for massive ZZ Ceti stars. II. The effects of crystallization on their pulsational properties
• TESS first look at evolved compact pulsators: Known ZZ Ceti stars of the southern ecliptic hemisphere as seen by TESS
• GD358: three decades of observations for the in-depth asteroseismology of a DBV star
• The Peculiar Pulsations of PY Vul
• High Resolution Spectroscopy of the Pulsating White Dwarf G29-38
• A new look at the pulsating DB white dwarf GD 358:Line-of-sight velocity measurements and constraints on model atmospheres
• Pulsational Mapping of Calcium Across the Surface of a White Dwarf
• A puzzling periodicity in the pulsating DA white dwarf G 117-B15A
• Deciphering the Pulsations of G 29-38 with Optical Time Series Spectroscopy
• Pulsating or not? A search for hidden pulsations below the red edge of the ZZ instability strip
• Asteroseismology of DAV star HS0507+0434B, including the core composition profiles
• Asteroseismology of DAV white dwarf stars and G29-38