Analysis of UBV-Photometric Observations of the Massive, Early-Type Binary System V729 Cyg (Cyg OB2 No. 5)

Abstract

We have analyzed photometric UBV light curves of the massive eclipsing binary system V729 Cyg which lies in the Cyg OB2 stellar association. The observations were made at the Abastumani Astrophysical Observatory in 1983–2003 as part of a program for studying binary systems of early types. The system V729 Cyg is a spectroscopic binary and consists of Of-stars. Effects associated with the collision of stellar winds are observed in it. Various researchers have assumed previously that the binary system is at an evolutionary stage of conversion into a WR+O system. The light curves have been analyzed by a synthesis method in terms of a Roche model using our own computer code analogous to the standard Wilson-Devinney code. This analysis shows that the binary system has a contact configuration and an orbital inclination of about 66 degrees. The absolute parameters of the components are estimated to be M 1 = 30.4M ⨀ , M 2 = 9.2M ⨀, R 1 = 24.6 R ⨀ , and R 2 = 13.8R ⨀ .