V772 Cas: an ellipsoidal HgMn star in an eclipsing binary

Abstract

The late B-type star V772 Cas (HD 10260) was previously suspected to be a rare example of a magnetic chemically peculiar star in an eclipsing binary system. Photometric observations of this star obtained by the TESS satellite show clear eclipses with a period of 5.0137 d accompanied by a significant out-of-eclipse variation with the same period. High-resolution spectroscopy reveals V772 Cas to be an SB1 system, with the primary component rotating about a factor two slower than the orbital period and showing chemical peculiarities typical of non-magnetic HgMn chemically peculiar stars. This is only the third eclipsing HgMn star known and, owing to its brightness, is one of the very few eclipsing binaries with chemically peculiar components accessible to detailed follow-up studies. Taking advantage of the photometric and spectroscopic observations available for V772 Cas, we performed modelling of this system with the PHOEBE code. This analysis provided fundamental parameters of the components and demonstrated that the out-of-eclipse brightness variation is explained by the ellipsoidal shape of the evolved, asynchronously rotating primary. This is the first HgMn star for which such variability has been definitively identified.

14 pages, 13 figures; accepted for publication in MNRAS

References in corpus (20)

• The Transiting Exoplanet Survey Satellite
• Astrophysics Source Code Library
• Stellar magnetism: empirical trends with age and rotation
• Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
• Physics Of Eclipsing Binaries. II. Towards the Increased Model Fidelity
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• emcee v3: A Python ensemble sampling toolkit for affine-invariant MCMC
• How mergers magnetise massive stars
• Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
• The dependence of convective core overshooting on stellar mass: reality check, and additional evidence
• Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades
• Hyperfine Splitting in the VALD Database of Spectral-line Parameters
• The BinaMIcS project: understanding the origin of magnetic fields in massive stars through close binary systems
• An empirical temperature calibration for the Delta a photometric system. II. The A-type and mid F-type star
• HD 99458: First time ever Ap-type star as a $\delta$ Scuti pulsator in a short period eclipsing binary?
• MOBSTER -- III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic 'identical twin'
• A Spectroscopic and Photometric Investigation of the Mercury-Manganese Star KIC 6128830
• Neon Abundances of B-stars in the Solar Neighborhood
• The nature of the photometric variability of HgMn stars: A test of simulated light curves of ϕ Phe against the TESS data
• Compositional differences between the component stars of eclipsing close binary systems showing chemical peculiarities