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arXiv · 1009.1873

SOPHIE velocimetry of Kepler transit candidates. I. Detection of the low-mass white dwarf KOI-74b

David Ehrenreich·Anne-Marie Lagrange·François Bouchy·Christian Perrier·Guillaume Hébrard·Isabelle Boisse·Xavier Bonfils·Luc Arnold·Xavier Delfosse·Morgan Desort·Rodrigo F. Díaz·Anne Eggenberger·Thierry Forveille·Christophe Lovis·Claire Moutou·Francesco Pepe·Frédéric Pont·Nuno C. Santos·Alexandre Santerne·Damien Ségransan·Stéphane Udry·Alfred Vidal-Madjar
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Abstract

The Kepler mission has detected transits and occultations of a hot compact object around an early-type star, the Kepler Object of Interest KOI 74. The mass of this transiting object was photometrically assessed in a previous study using the presence of the relativistic beaming effect (so-called `Doppler boosting') in the light curve. Our aim was to provide a spectroscopic validation of this pioneering approach. We measured the radial velocity variations of the A1V star KOI 74 with the SOPHIE spectrograph at the 1.93-m telescope of the Observatoire de Haute-Provence (France). Radial velocity measurements of this star are challenging because of the high level of stellar pulsations and the few available spectral lines. Using a technique dedicated to early-type main-sequence stars, we measured radial velocity variations compatible with a companion of mass 0.252+/-0.025 Msun, in good agreement with the value derived from the Kepler light curve. This work strengthens the scenario suggesting that KOI 74 is a blue straggler orbited by a stellar core despoiled of its envelope, the low-mass white dwarf KOI 74b.

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David Ehrenreich, Anne-Marie Lagrange, François Bouchy, Christian Perrier, Guillaume Hébrard, Isabelle Boisse, Xavier Bonfils, Luc Arnold, Xavier Delfosse, Morgan Desort, Rodrigo F. Díaz, Anne Eggenberger, Thierry Forveille, Christophe Lovis, Claire Moutou, Francesco Pepe, Frédéric Pont, Nuno C. Santos, Alexandre Santerne, Damien Ségransan, Stéphane Udry, Alfred Vidal-Madjar. 2010-10-27. SOPHIE velocimetry of Kepler transit candidates. I. Detection of the low-mass white dwarf KOI-74b. https://doi.org/10.1051/0004-6361%2F201015729

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