Relativistic apsidal motion in eccentric eclipsing binaries ^*

¹ Astronomical Institute, Faculty of Mathematics and Physics, Charles University Prague, 18000 Praha 8, V Holešovičkách 2, Czech Republic e-mail: wolf@cesnet.cz
² Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain e-mail: claret@iaa.es
³ Astronomical Institute, Academy of Sciences, Fričova 298, 25165 Ondřejov, Czech Republic
⁴ Johann Palisa Observatory and Planetarium, Technical University Ostrava, 70833 Ostrava, Czech Republic
⁵ Private Observatory, Velká Úpa 193, 54221 Pec pod Sněžkou, Czech Republic
⁶ Private Observatory, Výpustky 5, 61400 Brno, Czech Republic
⁷ Observatory Valašské Meziříčí, Vsetínská 78, 75701 Valašské Meziříčí, Czech Republic

Received: 16 January 2009
Accepted: 3 October 2009

Abstract

Context. The study of apsidal motion in detached eclipsing binary systems is known to be an important source of information about stellar internal structure as well as the possibility of verifying of General Relativity outside the Solar System.

Aims. As part of the long-term Ondřejov and Ostrava observational projects, we aim to measure precise times of minima for eccentric eclipsing binaries, needed for the accurate determination of apsidal motion, providing a suitable test of the effects of General Relativity.

Methods. About seventy new times of minimum light recorded with photoelectric or CCD photometers were obtained for ten eccentric-orbit eclipsing binaries with significant relativistic apsidal motion. Their O–C diagrams were analysed using all reliable timings found in the literature, and new or improved elements of apsidal motion were obtained.

Results. We confirm very long periods of apsidal motion for all systems. For BF Dra and V1094 Tau, we present the first apsidal-motion solution. The relativistic effects are dominant, representing up to 100% of the total observable apsidal-motion rate in several systems. The theoretical and observed values of the internal structure constant k₂ were compared for systems with lower relativistic contribution. Using the light-time effect solution, we predict a faint third component for V1094 Tau orbiting with a short period of about 8 years.