Pulsation in carbon-atmosphere white dwarfs: A new chapter in white dwarf asteroseismology

TL;DR

This paper explores the pulsation potential of carbon-atmosphere white dwarfs, demonstrating theoretical predictions and observational discoveries, including the first detection of g-mode pulsations in a magnetic white dwarf, expanding asteroseismology.

Contribution

It provides the first evidence of g-mode pulsations in a magnetic carbon-atmosphere white dwarf, opening a new asteroseismological window for white dwarf studies.

Findings

Detection of luminosity variations in SDSS J1426+5752.

Confirmation that SDSS J1426+5752 is a pulsating magnetic white dwarf.

Theoretical prediction of pulsations in certain parameter regions.

Abstract

We present some of the results of a survey aimed at exploring the asteroseismological potential of the newly-discovered carbon-atmosphere white dwarfs. We show that, in certains regions of parameter space, carbon-atmosphere white dwarfs may drive low-order gravity modes. We demonstrate that our theoretical results are consistent with the recent exciting discovery of luminosity variations in SDSS J1426+5752 and some null results obtained by a team of scientists at McDonald Observatory. We also present follow-up photometric observations carried out by ourselves at the Mount Bigelow 1.6-m telescope using the new Mont4K camera. The results of follow-up spectroscopic observations at the MMT are also briefly reported, including the surprising discovery that SDSS J1426+5752 is not only a pulsating star but that it is also a magnetic white dwarf with a surface field near 1.2 MG. The discovery of $g$-mode pulsations in SDSS J1426+5752 is quite significant in itself as it opens a fourth asteroseismological "window", after the GW Vir, V777 Her, and ZZ Ceti families, through which one may study white dwarfs.