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The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156

Williams, Kurtis A. and Hermes, J. J. and Vanderbosch, Zachary P. (2022) The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156. Astronomical Journal, 164 (4). Art. No. 131. ISSN 0004-6256. doi:10.3847/1538-3881/ac8543.

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The distribution of white dwarf rotation periods provides a means for constraining angular momentum evolution during the late stages of stellar evolution, as well as insight into the physics and remnants of double degenerate mergers. Although the rotational distribution of low-mass white dwarfs is relatively well constrained via asteroseismology, that of high-mass white dwarfs, which can arise from either intermediate-mass stellar evolution or white dwarf mergers, is not. Photometric variability in white dwarfs due to rotation of a spotted star is rapidly increasing the sample size of high-mass white dwarfs with measured rotation periods. We present the discovery of 22.4 minute photometric variability in the light curve of EGGR 156, a strongly magnetic, ultramassive white dwarf. We interpret this variability as rapid rotation, and our data suggest that EGGR 156 is the remnant of a double degenerate merger. Finally, we calculate the rate of period change in rapidly-rotating, massive, magnetic WDs due to magnetic dipole radiation. In many cases, including EGGR 156, the period change is not currently detectable over reasonable timescales, indicating that these WDs could be very precise clocks. For the most highly-magnetic, rapidly-rotating massive WDs, such as ZTF J1901+1450 and RE J0317−853, the period change should be detectable and may help constrain the structure and evolution of these exotic white dwarfs.

Item Type:Article
Related URLs:
URLURL TypeDescription
Williams, Kurtis A.0000-0002-1413-7679
Hermes, J. J.0000-0001-5941-2286
Vanderbosch, Zachary P.0000-0002-0853-3464
Additional Information:This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The authors wish to recognize the significant contributions of David Doss to McDonald Observatory on the occasion of his retirement; his tireless efforts throughout his career enabled this research as well as that of multiple generations of white dwarf astronomers. The authors thank D. Winget and M. H. Montgomery for helpful discussions after the initial discovery of this object's variability. The authors also thank J. Farihi, P. Dufour, and M. Kilic for insightful discussions during the preparation of this manuscript. We are also grateful for the time and efforts of J. Kuhne, B. Roman, and the rest of the staff at McDonald Observatory for enabling remote observing with the Otto Struve Telescope during the COVID-19 pandemic. This material is based upon work supported by the National Science Foundation under grant No. AST-1910551.
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Gaia Multilateral AgreementUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20220916-663587000
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116995
Deposited By: Olivia Warschaw
Deposited On:29 Oct 2022 20:50
Last Modified:29 Oct 2022 20:50

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