Littlefair, S. P., Dhillon, V. S., Marsh, T. R., Gänsicke, B. T. (Boris T.), Baraffe, I. and Watson, C. A.. (2007) SDSS J150722.30+523039.8: a cataclysmic variable formed directly from a detached white dwarf/brown dwarf binary? Monthly Notices of the Royal Astronomical Society, Vol.381 (No.2). pp. 827-834. ISSN 0035-8711

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Abstract

We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J150722.30+523039.8 (hereafter SDSS J1507). This system has an orbital period of 66.61 min, placing it below the observed 'period minimum' for cataclysmic variables. We determine the system parameters via a parametrized model of the eclipse fitted to the observed lightcurve by chi(2) minimization. We obtain a mass ratio of q = 0.0623 +/- 0.0007 and an orbital inclination i = 83.degrees 63 +/- 0.degrees 05. The primary mass is M-w = 0.90 +/- 0.01M(circle dot). The secondary mass and radius are found to be M-r = 0.056 +/- 0.001M(circle dot) and R-r = 0.096 +/- 0.001R(circle dot), respectively. We find a distance to the system of 160 +/- 10 pc. The secondary star in SDSS J1507 has a mass substantially below the hydrogen burning limit, making it the second confirmed substellar donor in a cataclysmic variable. The very short orbital period of SDSS J1507 is readily explained if the secondary star is nuclearly evolved, or if SDSS J1507 formed directly from a detached white dwarf/brown dwarf binary. Given the lack of any visible contribution from the secondary star, the very low secondary mass and the low He i lambda 6678/H alpha emission-line ratio, we argue that SDSS J1507 probably formed directly from a detached white dwarf/brown dwarf binary. If confirmed, SDSS J1507 will be the first such system identified. The implications for binary star evolution, the brown dwarf desert and the common envelope phase are discussed.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley-Blackwell Publishing, Inc
ISSN:	0035-8711
Date:	21 October 2007
Volume:	Vol.381
Number:	No.2
Number of Pages:	8
Page Range:	pp. 827-834
Identification Number:	10.1111/j.1365-2966.2007.12285.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/31254

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