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arXiv · 2003.10450

An Isolated White Dwarf with 317-Second Rotation and Magnetic Emission

Joshua S. Reding·J. J. Hermes·Z. Vanderbosch·E. Dennihy·B. C. Kaiser·C. B. Mace·B. H. Dunlap·J. C. Clemens
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Abstract

We report the discovery of short-period photometric variability and modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72 (EPIC 228939929), a variable white dwarf star observed at long cadence in \textit{K2} Campaign 10. The behavior is associated with a magnetic ($B=5.0$ MG) spot on the stellar surface, making the $317.278$-second period a direct measurement of the stellar rotation rate. This object is therefore the fastest-rotating apparently isolated (without a stellar companion) white dwarf yet discovered, and the second found to exhibit chromospheric Balmer emission after GD 356, in which the emission has been attributed to a unipolar inductor mechanism driven by a possible rocky planet. We explore the properties and behavior of this object, and consider whether its evolution may hold implications for white dwarf mergers and their remnants.

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Joshua S. Reding, J. J. Hermes, Z. Vanderbosch, E. Dennihy, B. C. Kaiser, C. B. Mace, B. H. Dunlap, J. C. Clemens. 2020-03-23. An Isolated White Dwarf with 317-Second Rotation and Magnetic Emission. https://doi.org/10.3847/1538-4357%2Fab8239

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