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Abstract We report the discovery of an isolated white dwarf with a spin period of 70 s. We obtained high-speed photometry of three ultramassive white dwarfs within 100 pc and discovered significant variability in one. SDSS J221141.80+113604.4 is a 1.27M⊙(assuming a CO core) magnetic white dwarf that shows 2.9% brightness variations in the BG40 filter with a 70.32 ± 0.04 s period, becoming the fastest spinning isolated white dwarf currently known. A detailed model atmosphere analysis shows that it has a mixed hydrogen and helium atmosphere with a dipole field strength ofBd= 15 MG. Given its large mass, fast rotation, strong magnetic field, unusual atmospheric composition, and relatively large tangential velocity for its cooling age, J2211+1136 displays all of the signatures of a double white dwarf merger remnant. Long-term monitoring of the spin evolution of J2211+1136 and other fast-spinning isolated white dwarfs opens a new discovery space for substellar and planetary mass companions around white dwarfs. In addition, the discovery of such fast rotators outside of the ZZ Ceti instability strip suggests that some should also exist within the strip. Hence, some of the monoperiodic variables found within the instability strip may be fast-spinning white dwarfs impersonating ZZ Ceti pulsators.
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Photometric Monitoring of the ZZ Ceti Star PG 1541+651
Abstract The Kepler and K2 missions discovered multiple ZZ Ceti white dwarf pulsators that exhibit recurrent outbursts. These outbursting white dwarfs are near the red edge of the ZZ Ceti instability strip, suggesting that the phenomenon is physically related to the cessation of pulsations. We present multi-day ground-based monitoring of the poorly studied red-edge ZZ Ceti pulsator PG 1541+651. We do not detect any outbursts in our data. We do find that this pulsator has a very rich and time-variable spectrum of modes in its periodogram. The white dwarf lies in the northern continuous viewing zone of TESS; therefore, it has extensive archival light curves ripe for a detailed asteroseismic analysis of this star.
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- PAR ID:
- 10421846
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 7
- Issue:
- 6
- ISSN:
- 2515-5172
- Format(s):
- Medium: X Size: Article No. 122
- Size(s):
- Article No. 122
- Sponsoring Org:
- National Science Foundation
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