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Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

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Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

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Título Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2
Autor Williams, Kurtis
Winget, Donald Earl
Montgomery, Michael Houston
Dufour, Patrick
Kepler, Souza Oliveira
Hermes, James J.
Falcon, Ross E.
Winget, K. I.
Bolte, Michael
Rubin, Kate H. R.
Liebert, James
Abstract 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: Teff ≈ 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, heliumdominated 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.
Contido em The astrophysical journal. Bristol. Vol. 769, no. 2 (June 2013), 123, 11 p.
Assunto Anãs brancas
Estrelas magneticas
Fotometria estelar
Magnetismo estelar
[en] Stars: evolution
[en] Stars: individual (SDSS J103655.39+652252.2)
[en] Stars: magnetic field
[en] Stars: oscillations (including pulsations)
[en] White dwarfs
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/109077
Arquivos Descrição Formato
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