HD 159176: photospheric and wind-dominated light-curve analyses coupled to wind modelling

Abstract

HD 159176 is a hot, massive, non-eclipsing binary with a small-amplitude ellipsoidal variability. The existing velocity solution determines the ratio of the stellar masses. In the present article these radial velocities, coupled with one optical and two UV light curves derived from IUE images in bandpasses devoid of stellar wind lines, are solved simultaneously using the Wilson-Devinney light-curve synthesis code. Modelling of the C IV and N V wind-line profiles supports optically thick, extended and eclipsing winds with a mass-loss rate of 3.0 x 10-6 Mo yr- 1 from each star. Light curves derived from bandpasses isolating the C IV and N V wind lines clearly show wind eclipses. As an exercise, the WD code is employed to calculate a tentative solution to these wind light curves. Naturally, the input parameter values to that code have been tailored to mimic wind behaviour as closely as possible. A new code modelling wind eclipses is under construction and aspires to the determination of accurate inclinations and thus the individual stellar masses for a number of hot, photospherically non-eclipsing binaries.