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

• Published in: The Astrophysical journal Vol. 683; no. 2; pp. L167 - L170
• Main Authors: Dufour, P, Fontaine, G, Liebert, James, Williams, Kurtis, Lai, David K
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 20.08.2008; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Stellar abundance; Magnetic stars; stars: abundances-stars: atmospheres-stars: individual (SDSS J1426+5752); Pulsating variable stars; Magnetic fields; stars: magnetic fields
• ISSN: 1538-4357; 0004-637X; 1538-4357
• DOI: 10.1086/591672

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 [image] MG, based on obvious Zeeman components seen in several carbon lines. We also detect the presence of a Zeeman-splitted He i [lambda]4471 line, which is an indicator of the presence of a nonnegligible 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 rapidly oscillating Ap star.