The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1
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Author
Littlefair, S.P.
Casewell, S.L.
Parsons, S.G.
Dhillon, V. S.
Marsh, T.R.
Gansicke, B.T.
Bloemen, S.
Catalan, Silvia
Irawati, P.
Hardy, L.K.
Mcallister, M.
Bours, M.C.P.
Richichi, A.
Burleigh, M.R.
Burningham, B.
Breedt, E.
Kerry, P.
Attention
2299/16769
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