Apsidal motion in eccentric eclipsing binaries: CW Cephei, V478 Cygni, AG Persei, and IQ Persei

¹ Astronomical Institute, Charles University of Prague, 180 00 Praha 8, V Holešovičkách 2, Czech Republic e-mail: wolf@cesnet.cz
² Johann Palisa Observatory and Planetarium, Technical University Ostrava, 708 33 Ostrava, Czech Republic
³ Department of Astronomy and Space Sciences, Ege University, Faculty of Science, 35100 Bornova, Izmir, Turkey
⁴ Astronomical Institute, Academy of Sciences, 251 65 Ondřejov, Czech Republic
⁵ Institute of Theoretical Physics and Astrophysics, Masaryk University, 611 37 Brno, Czech Republic
⁶ Private Observatory, Velká Úpa 193, 542 21 Pec pod Sněžkou, Czech Republic
⁷ Private Observatory, 664 31 Lelekovice 393, Czech Republic

Received: 30 March 2006
Accepted: 6 June 2006

Abstract

Aims.About thirty new times of minimum light recorded with photoelectric or CCD photometers were obtained for four early-type eccentric-orbit eclipsing binaries CW Cep (, ), V478 Cyg (), AG Per (), and IQ Per ().

Methods.Their  diagrams were analysed using all reliable timings found in the literature, and elements of apsidal motion were improved.

Results.We confirm relatively short periods of apsidal motion of about 46, 27, 76, and 124 years for CW Cep, V478 Cyg, AG Per, and IQ Per, respectively. The corresponding internal structure constants, log k₂, are then found to be –2.12, –2.25, –2.15, and –2.36, under the assumption that the component stars rotate pseudosynchronously. The relativistic effects are negligible, being up to 8% of the total apsidal motion rate in all systems. Using the light-time effect solution, we have predicted a faint third component orbiting with a period of about 39 years for CW Cep.