Harmanec, P. ; Koubský, P. ; Nemravová, J. A. ; Royer, F. ; Briot, D. ; North, P. ; Lampens, P. ; Frémat, Y. ; Yang, S. ; Božic, H. ; Kotková, L. ; Škoda, P. ; Šlechta, M. ; Korcáková, D. ; Wolf, M. ; Zasche, P.

published in Astronomy and Astrophysics, 573, pp. A107 (2015)

Abstract: Reliable determination of the basic physical properties of hot emission-line binaries with Roche-lobe filling secondaries is important for developing the theory of mass exchange in binaries. It is a very hard task, however, which is complicated by the presence of circumstellar matter in these systems. So far, only a small number of systems with accurate values of component masses, radii, and other properties are known. Here, we report the first detailed study of a new representative of this class of binaries, BR CMi, based on the analysis of radial velocities and multichannel photometry from several observatories, and compare its physical properties with those for other well-studied systems. BR CMi is an ellipsoidal variable seen under an intermediate orbital inclination of ˜ 51°, and it has an orbital period of 12.^d919059(15) and a circular orbit. We used the disentangled component spectra to estimate the effective temperatures 9500(200) K and 4655(50) K by comparing them with model spectra. They correspond to spectral types B9.5e and G8III. We also used the disentangled spectra of both binary components as templates for the 2D cross-correlation to obtain accurate radial velocities and a reliable orbital solution. Some evidence of a secular period increase at a rate of (1.1 ± 0.5) s per year was found. This, together with a very low mass ratio of 0.06 and a normal mass and radius of the mass gaining component, indicates that BR CMi is in a slow phase of the mass exchange after the mass-ratio reversal. It thus belongs to a still poorly populated subgroup of Be stars for which the origin of Balmer emission lines is safely explained as a consequence of mass transfer between the binary components. Based on new spectroscopic and photometric observations from the following instruments: Elodie spectrograph of the Haute Provence Observatory, France; CCD coudé spectrograph of the Astronomical Institute AS CR at Ondrejov, Czech Republic; CCD coudé spectrograph of the Dominion Astrophysical Observatory, Canada; HERMES spectrograph attached to the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias; 7-C photometer attached to the Mercator Telescope, La Palma, UBV photometers at Hvar and Sutherland, and Hp photometry from the ESA Hipparcos mission.Appendices are available in electronic form at http://www.aanda.org

DOI: 10.1051/0004-6361/201424640
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