Mon. Not. R. Astron. Soc., 471, 948-961 (2017/October-2)
WD 1202-024: the shortest-period pre-cataclysmic variable.
RAPPAPORT S., VANDERBURG A., NELSON L., GARY B.L., KAYE T.G., KALOMENI B., HOWELL S.B., THORSTENSEN J.R., LACHAPELLE F.-R., LUNDY M. and ST-ANTOINE J.
Abstract (from CDS):
Among the 28 000 targeted stars in K2 Field 10 is the white dwarf WD 1202-024 (EPIC 201283111), first noted in the SDSS survey (SDSS 120515.80-024222.7). We have found that this hot white dwarf (Teff ≃ 22 640 K) is in a very close orbit (P ≃ 71 min) with a star of near brown-dwarf mass ≃0.061 M☉. This period is very close to, or somewhat below, the minimum orbital period of cataclysmic variables with H-rich donor stars. However, we find no evidence that this binary is currently, or ever was, transferring mass from the low-mass companion to the white dwarf. We therefore tentatively conclude that this system is still in the pre-cataclysmic variable phase, having emerged from a common envelope some 50 ± 20 Myr ago. Because of the 29-min integration time of K2, we use follow-up ground-based photometry to better evaluate the eclipsing light curve. We also utilize the original SDSS spectra, in approximately 15-min segments, to estimate the radial velocity of the white dwarf in its orbit. An analysis of the light curve, with supplementary constraints, leads to the following system parameters: Mwd ≃ 0.415 ± 0.028 M☉, Rwd ≃ 0.021 ± 0.001 R☉, Mcom ≃ 0.061 ± 0.010 M☉ and Rcom ≃ 0.088 ± 0.005 R☉ where the subscripts 'wd' and 'com' refer to the white dwarf and low-mass companion, respectively. If our interpretation of this system as a pre-CV is correct, it has the shortest period of any such system yet found and should become a compact CV in less than 250 Myr.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
binaries: eclipsing - binaries: general - stars: dwarf novae - novae, cataclysmic variables - white dwarfs - white dwarfs
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