The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1

S.P. Littlefair, S.L. Casewell, S.G. Parsons, V. S. Dhillon, T.R. Marsh, B.T. Gansicke, S. Bloemen, Silvia Catalan, P. Irawati, L.K. Hardy, M. Mcallister, M.C.P. Bours, A. Richichi, M.R. Burleigh, B. Burningham, E. Breedt, P. Kerry

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Abstract

We present high time resolution SDSS-g′ and SDSS-z′ light curves of the primary eclipse in SDSS J141126.20+200911.1, together with time-resolved X-Shooter spectroscopy and near-infrared (NIR) JHKs photometry. Our observations confirm the substellar nature of the companion, making SDSS J141126.20+200911.1 the first eclipsing white dwarf/brown dwarf binary known. We measure a (white dwarf model dependent) mass and radius for the brown dwarf companion of M2 = 0.050 ± 0.002 M⊙ and R2 = 0.072 ± 0.004 M⊙, respectively. The lack of a robust detection of the companion light in the z′-band eclipse constrains the spectral type of the companion to be later than L5. Comparing the NIR photometry to the expected white dwarf flux reveals a clear Ks-band excess, suggesting a spectral type in the range L7–T1. The radius measurement is consistent with the predictions of evolutionary models, and suggests a system age in excess of 3 Gyr. The low companion mass is inconsistent with the inferred spectral type of L7–T1, instead predicting a spectral type nearer T5. This indicates that irradiation of the companion in SDSS J141126.20+200911.1 could be causing a significant temperature increase, at least on one hemisphere
Original languageEnglish
Pages (from-to)2106-2115
JournalMonthly Notices of the Royal Astronomical Society
Volume445
Issue number2
Early online date15 Oct 2014
DOIs
Publication statusPublished - 1 Dec 2014

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