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Title: NLTT 5306: the shortest period detached white dwarf plus brown dwarf binary
Authors: Steele, P. R.
Saglia, R. P.
Burleigh, Matthew R.
Marsh, T. R.
Gaensicke, B. T.
Lawrie, K.
Cappetta, M.
Girven, J.
Napiwotzki, R.
First Published: 12-Jan-2013
Publisher: Oxford University Press for Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2013, 429 (4), pp. 3492-3500
Abstract: We have spectroscopically confirmed a brown dwarf mass companion to the hydrogen atmosphere white dwarf NLTT 5306. The white dwarf's atmospheric parameters were measured using the Sloan Digital Sky Survey and X-shooter spectroscopy as Teff = 7756 ± 35 K and log(g) = 7.68 ± 0.08, giving a mass for the primary of MWD = 0.44 ± 0.04 M⊙ at a distance of 71 ± 4 pc with a cooling age of 710 ± 50 Myr. The existence of the brown dwarf secondary was confirmed through the near-infrared arm of the X-shooter data and a spectral type of dL4–dL7 was estimated using standard spectral indices. Combined radial velocity measurements from the Sloan Digital Sky Survey, X-shooter and the Hobby–Eberly Telescope's High Resolution Spectrograph of the white dwarf give a minimum mass of 56 ± 3 MJup for the secondary, confirming the substellar nature. The period of the binary was measured as 101.88 ± 0.02 min using both the radial velocity data and i′-band variability detected with the Isaac Newton Telescope. This variability indicates ‘day’ side heating of the brown dwarf companion. We also observe Hα emission in our higher resolution data in phase with the white dwarf radial velocity, indicating that this system is in a low level of accretion, most likely via a stellar wind. This system represents the shortest period white dwarf+brown dwarf binary and the secondary has survived a stage of common envelope evolution, much like its longer period counterpart, WD 0137−349. Both systems likely represent bona fide progenitors of cataclysmic variables with a low-mass white dwarf and a brown dwarf donor.
DOI Link: 10.1093/mnras/sts620
ISSN: 0035-8711
eISSN: 1365-2966
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the authors, 2013, Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License ( ), which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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