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| Paper: |
Discovery of Pulsations in He-core, Extremely Low Mass White Dwarfs |
| Volume: |
469, 18th European White Dwarf Workshop (EUROWD12) |
| Page: |
57 |
| Authors: |
Hermes, J. J.; Montgomery, M. H.; Winget, D. E.; Brown, W. R.; Kilic, M.; Kenyon, S. J.; Harrold, S. T.; Bell, K.; Pelletier, J.; Rostopchina, A. |
| Abstract: |
After an extensive search, we announce the discovery of the first three extremely low mass (ELM, ≤ 0.25 M☉), putatively He-core pulsating white dwarfs (WDs). The objects are by far the coolest and the lowest-mass pulsating WD known. The first to be published, SDSS J1840+6423 (Hermes et al. 2012), has Teff = 9140±170 K and log g = 6.22±0.06, which corresponds to a mass of ∼ 0.17 M☉. The second and third pulsating ELM WDs have similarly low masses. SDSS J1112+1117 has Teff = 9400±490 K and a log g = 5.99±0.12. SDSS J1518+0658 has Teff = 9810±320 K and a log g = 6.66±0.06. These low-mass pulsating WDs greatly extend the DAV (or ZZ Ceti) instability strip, and begin to bridge the gap in surface gravity between WDs and main-sequence stars. Consistent with the expectation that these ELM WDs are the product of binary evolution, all three of these stars have an unseen binary companion, with 4.2–14.6 hr orbital periods, in each case most likely another WD. |
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