Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2
- Department of Physics and Astronomy, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX 75429 (United States)
- Department of Astronomy, University of Texas, 1 University Station C1400, Austin, TX 78712 (United States)
- Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7 (Canada)
- Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500 Porto Alegre 91501-970, RS (Brazil)
- UCO/Lick Observatory, University of California, 1156 High St., Santa Cruz, CA 95064 (United States)
- Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
- Emeritus, Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)
We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T {sub eff} ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.
- OSTI ID:
- 22342054
- Journal Information:
- Astrophysical Journal, Vol. 769, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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