SDSS J142625.71+575218.3: The First Pulsating White Dwarf with a Large Detectable Magnetic Field

TL;DR

This paper reports the discovery of the first pulsating white dwarf with a large, detectable magnetic field, providing new insights into magnetic effects on white dwarf pulsations.

Contribution

It presents the first detection of a strong magnetic field in a pulsating white dwarf, linking magnetic fields with pulsation properties in Hot DQ stars.

Findings

Surface magnetic field of ~1.2 MG detected

Presence of helium in the atmosphere confirmed

First example of a pulsating white dwarf with a large magnetic field

Abstract

We report the discovery of a strong magnetic field in the unique pulsating carbon-atmosphere white dwarf SDSS J142625.71+575218.3. From spectra gathered at the MMT and Keck telescopes, we infer a surface field of B_s ~1.2 MG, based on obvious Zeeman components seen in several carbon lines. We also detect the presence of a Zeeman-splitted He I 4471 line, which is an indicator of the presence of a non-negligible amount of helium in the atmosphere of this Hot DQ star. This is important for understanding its pulsations, as nonadabatic theory reveals that some helium must be present in the envelope mixture for pulsation modes to be excited in the range of effective temperature where the target star is found. Out of nearly 200 pulsating white dwarfs known today, this is the first example of a star with a large detectable magnetic field. We suggest that SDSS J142625.71+575218.3 is the white dwarf equivalent of a roAp star.