Light curve analysis of Hipparcos data for the massive O-type eclipsing binary UW CMa

Abstract Hipparcos photometric data for the massive O-type binary UW CMa were analysed within the framework of the Roche model. Photometric solutions were obtained for five mass ratios in the q  =  M 2 / M 1  = 0.5–1.5 range. The system is found to be in a contact configuration. Independently of q , the best-fitting model solutions correspond to the orbital inclination i  ∼ 71° and the temperature of the secondary component T 2  ∼ 33500 K, at the fixed temperature of the primary T 1  = 33750 K. Considering that the spectrum of the secondary is very weak, photometric solutions corresponding to the contact configuration favor the mass ratio q smaller than unity (in which case the luminosity of the secondary is smaller than that of the primary). The absolute parameters of the system are estimated for different values of the mass ratio.