An Isolated White Dwarf with 317 s Rotation and Magnetic Emission
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 K2 Campaign 10. The behavior is associated with a magnetic (B = 5.0 MG) spot on the stellar surface, making the 317.278 s 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2020
- DOI:
- 10.3847/1538-4357/ab8239
- arXiv:
- arXiv:2003.10450
- Bibcode:
- 2020ApJ...894...19R
- Keywords:
-
- White dwarf stars;
- Magnetic variable stars;
- Extrasolar rocky planets;
- Stellar mergers;
- Stellar rotation;
- 1799;
- 996;
- 511;
- 2157;
- 1629;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 11 pages, 6 figures, 3 tables. Accepted for publication in ApJ