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

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.

[1]  V. S. Dhillon,et al.  ULTRASPEC: a high-speed imaging photometer on the 2.4-m Thai National Telescope , 2014, 1408.2733.

[2]  V. S. Dhillon,et al.  The planets around nn serpentis: still there , 2013, 1310.1391.

[3]  J. Winters,et al.  THE SOLAR NEIGHBORHOOD. XXXII. THE HYDROGEN BURNING LIMIT, , 2013, 1312.1736.

[4]  S. Dreizler,et al.  The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion , 2013, 1312.5088.

[5]  D. O. Astronomy,et al.  Exploring the Milky Way stellar disk - A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood , 2013, 1309.2631.

[6]  H. Ludwig,et al.  Spectroscopic analysis of DA white dwarfs with 3D model atmospheres , 2013, 1309.0886.

[7]  S. Littlefair,et al.  A magnetic white dwarf in a detached eclipsing binary , 2013, 1308.4423.

[8]  M. Kilic,et al.  LIMB-DARKENING COEFFICIENTS FOR ECLIPSING WHITE DWARFS , 2013, 1301.7091.

[9]  Daniel Foreman-Mackey,et al.  emcee: The MCMC Hammer , 2012, 1202.3665.

[10]  C. Copperwheat,et al.  An accurate mass and radius measurement for an ultracool white dwarf , 2012, 1207.5393.

[11]  Michael C. Liu,et al.  THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, , 2012, 1201.2465.

[12]  P. Kerry,et al.  A precision study of two eclipsing white dwarf plus M dwarf binaries , 2011, 1111.5694.

[13]  Boris T. Gänsicke,et al.  DA white dwarfs in Sloan Digital Sky Survey Data Release 7 and a search for infrared excess emission , 2011 .

[14]  V. S. Dhillon,et al.  Two planets orbiting the recently formed post-common envelope binary NN Serpentis , 2010, 1010.3608.

[15]  K. Williams,et al.  A GRAVITATIONAL REDSHIFT DETERMINATION OF THE MEAN MASS OF WHITE DWARFS. DA STARS , 2010, 1002.2009.

[16]  R. Davies,et al.  Astronomical Society of the Pacific Conference Series , 2010 .

[17]  Michael Wegner,et al.  Ground-based and Airborne Instrumentation for Astronomy III , 2010 .

[18]  David A. Golimowski,et al.  THE 0.8–14.5 μm SPECTRA OF MID-L TO MID-T DWARFS: DIAGNOSTICS OF EFFECTIVE TEMPERATURE, GRAIN SEDIMENTATION, GAS TRANSPORT, AND SURFACE GRAVITY , 2009, 0906.2991.

[19]  R. F. Jameson,et al.  High-resolution optical spectroscopy of Praesepe white dwarfs , 2009, 0901.4464.

[20]  Maurizio Salaris,et al.  SEMI-EMPIRICAL WHITE DWARF INITIAL–FINAL MASS RELATIONSHIPS: A THOROUGH ANALYSIS OF SYSTEMATIC UNCERTAINTIES DUE TO STELLAR EVOLUTION MODELS , 2008, 0807.3567.

[21]  I. Kamp,et al.  COOL STARS, STELLAR SYSTEMS AND THE SUN , 2009 .

[22]  I. Ribas,et al.  The initial–final mass relationship of white dwarfs revisited: effect on the luminosity function and mass distribution , 2008, 0804.3034.

[23]  S. O. Kepler,et al.  SDSS DR7 WHITE DWARF CATALOG , 2007, 1212.1222.

[24]  V. S. Dhillon,et al.  ULTRACAM: an ultrafast, triple-beam CCD camera for high-speed astrophysics , 2007 .

[25]  I. McLean,et al.  Ground-based and Airborne Instrumentation for Astronomy , 2006 .

[26]  James Liebert,et al.  A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4 , 2006, astro-ph/0606700.

[27]  Pierre Bergeron,et al.  Calibration of Synthetic Photometry Using DA White Dwarfs , 2005 .

[28]  U. Southampton,et al.  ULTRACAM photometry of the eclipsing cataclysmic variables XZ Eri and DV UMa , 2004, astro-ph/0409184.

[29]  F. Allard,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003, astro-ph/0302293.

[30]  A. Burrows,et al.  Theoretical Spectra and Atmospheres of Extrasolar Giant Planets , 2002, astro-ph/0210216.

[31]  Johns Hopkins University,et al.  Characterization of M, L, and T Dwarfs in the Sloan Digital Sky Survey , 2002, astro-ph/0204065.

[32]  J. Cepa,et al.  The effects of seeing on Sérsic profiles – II. The Moffat PSF , 2001, astro-ph/0109067.

[33]  P. Green,et al.  A Comparative Study of the Mass Distribution of Extreme-Ultraviolet-selected White Dwarfs , 1999, astro-ph/9901027.

[34]  J. Lunine,et al.  Reflected Spectra and Albedos of Extrasolar Giant Planets. I. Clear and Cloudy Atmospheres , 1998, astro-ph/9810073.

[35]  R. J. Hanisch,et al.  Astronomical Data Analysis Software and Systems X , 2014 .

[36]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .