HS 0705+6700: A new eclipsing sdB binary *,**
Dr. Remeis-Sternwarte Bamberg, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstraße 7, 96049 Bamberg, Germany
2 Isaac Newton Group of Telescopes, 37800 Santa Cruz de La Palma, Canary Islands, Spain e-mail: firstname.lastname@example.org
3 University of Tromsø, Department of Physics, 9037 Tromsø, Norway e-mail: email@example.com
4 Institut für Astronomie und Astrophysik, Universität Tübingen, Waldhäuser Straße 64, 72076 Tübingen, Germany e-mail: firstname.lastname@example.org
5 Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244 Cracow, Poland e-mail: email@example.com
Corresponding author: H. Drechsel, firstname.lastname@example.org
Accepted: 26 September 2001
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.
Key words: stars: subdwarfs / binaries: eclipsing / binaries: spectroscopic / stars: early-type / stars: fundamental parameters / stars: individual: HS 0705+6700
Based on observations collected at the German-Spanish Astronomical Center (DSAZ), Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.
© ESO, 2001