HS 0705+6700: A new eclipsing sdB binary

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 8263.87 s, the mass ratio of the system , the inclination of 84 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 km s-1 and a mass function of are determined. A spectroscopic analysis of the blue spectra results in K, , and . These characteristics are typical for sdB stars, as is its mass of 0.48 . According to its mass (0.13 ) and radius (0.19 ), 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.