2001A&A...379..893D

We report the discovery of an eclipsing binary - HS 0705+6700 - being an sdB star with a faint companion. From its light curve the orbital period of 8263.87s, the mass ratio of the system q=0.28, the inclination of 84.4deg and other system parameters are derived. The companion does not contribute to the optical light of the system except through a strong reflection effect. The semi-amplitude of the radial velocity curve K₁=85.8km/s and a mass function of f(m)=0.00626M_☉ are determined. A spectroscopic analysis of the blue spectra results in T_eff=28800K, logg=5.40, and log(n_He/n_H)=-2.68. These characteristics are typical for sdB stars, as is its mass of 0.48M_☉. According to its mass (0.13M_☉) and radius (0.19R_☉), the companion is an M dwarf. The primary is in a core helium burning phase of evolution, and the system must have gone through a common envelope stage when the primary was near the tip of the red giant branch.