1. EPIC 216747137: a new HW Vir eclipsing binary with a massive sdOB primary and a low-mass M-dwarf companion
- Author
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Luigi Mancini, U. Heber, David Kilkenny, Horst Drechsel, Roy Ostensen, Andreas Irrgang, J. H. Telting, V. Schaffenroth, J. Vos, Roberto Silvotti, and Simona Ciceri
- Subjects
Physics ,010504 meteorology & atmospheric sciences ,Settore FIS/05 ,Stellar rotation ,FOS: Physical sciences ,binaries: eclipsing ,Binary number ,Astronomy and Astrophysics ,Astrophysics ,EPIC ,Orbital period ,01 natural sciences ,Astrophysics - Solar and Stellar Astrophysics ,stars: horizontal branch ,stars: individual: EPIC 216747137 ,Space and Planetary Science ,Primary (astronomy) ,0103 physical sciences ,Low Mass ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
EPIC 216747137 is a new HW~Virginis system discovered by the Kepler spacecraft during its K2 "second life". Like the other HW Vir systems, EPIC 216747137 is a post-common-envelope eclipsing binary consisting of a hot subluminous star and a cool low-mass companion. The short orbital period of 3.87 hours produces a strong reflection effect from the secondary (~9% in the R band). Together with AA Dor and V1828 Aql, EPIC 216747137 belongs to a small subgroup of HW Vir systems with a hot evolved sdOB primary. We find the following atmospheric parameters for the hot component: Teff=40400$\pm$1000 K, logg=5.56$\pm$0.06, log(N(He)/N(H))=$-$2.59$\pm$0.05. The sdOB rotational velocity vsini=51$\pm$10 km/s implies that the stellar rotation is slower than the orbital revolution and the system is not synchronized. When we combine photometric and spectroscopic results with the Gaia parallax, the best solution for the system corresponds to a primary with a mass of about 0.62 Msun close to, and likely beyond, the central helium exhaustion, while the cool M-dwarf companion has a mass of about 0.11 Msun., 16 pages, 16 figures, MNRAS, accepted for publication
- Published
- 2020