STUDY OF ECLIPSING BINARY AND MULTIPLE SYSTEMS IN OB ASSOCIATIONS. II. THE CYGNUS OB REGION: V443 Cyg, V456 Cyg, AND V2107 Cyg

Abstract

Three presumably young eclipsing binary systems in the direction of the Cygnus OB1, OB3, and OB9 associations are studied. Component spectra are reconstructed and their orbits are determined using light curves and spectra disentangling techniques. V443 Cyg and V456 Cyg have circular orbits while the light curve of V2107 Cyg imposes a slightly eccentric orbit (e = 0.045 +/- 0.03). V443 Cyg harbors F-type stars, not young early-A stars as previously suggested in the literature based solely on photometry. It appears to be situated in the foreground (distance 0.6 +/- 0.2 kpc) of the young stellar populations in Cygnus. V456 Cyg, at a distance of 0.50 +/- 0.03 kpc, consists of a slightly metal-weak A-type star and an early-F star. The age of both systems, on or very near to the main sequence, remains uncertain by an order of magnitude. V2107 Cyg is a more massive system (8.9 +/- 2 and 4.5 +/- 1.2M(circle dot)) at 1.5 +/- 0.5 kpc and, also kinematically, a strong candidate-member of Cyg OB1. The more massive component is slightly evolved and appears to undergo non-radial beta Cep-type pulsations. The Doppler signal of the secondary is barely detectable. A more extensive, asteroseismological study is necessary to fix masses more precisely. Nevertheless, the position of the primary in the H-R diagram confines the age reasonably well to 20 +/- 5 Myr, indicating that for Cyg OB1 has a similar extent of star formation history as that established for Cyg OB2.