EPIC 216747137: a new HW Vir eclipsing binary with a massive sdOB primary and a low-mass M-dwarf companion

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

References in corpus (13)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• The unWISE Catalog: Two Billion Infrared Sources from Five Years of WISE Imaging
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• SkyMapper Southern Survey: Second Data Release (DR2)
• CERES: A Set of Automated Routines for Echelle Spectra
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• Gravity and limb-darkening coefficients for compact stars: DA, DB, and DBA eclipsing white dwarfs
• Kepler detection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC10001893
• An eclipsing post common-envelope system consisting of a pulsating hot subdwarf B star and a brown dwarf companion
• Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II. Kinematics
• Hot Subdwarf All Southern Sky Fast Transit Survey with the Evryscope
• No close companions to a sample of bright sdB stars

Cited by in corpus (3)

• A hot subdwarf-white dwarf super-Chandrasekhar candidate supernova Ia progenitor
• A Catalogue of Potential Post Common Envelope Binaries
• Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well defined rotational splitting