Eclipsing high-mass binaries

Abstract

We present the first results of a comprehensive photometric O-star survey performed with a robotic twin refractor at the Universitätssternwarte Bochum located near Cerro Armazones in Chile. For three high-mass stars, Pismis 24-1, CPD − 51° 8946, and HD 319702, we determined the period through the Lafler-Kinman algorithm and modelled the light curves within the framework of the Roche geometry. For Pismis 24-1, a previously known eclipsing binary, we provide the first light curves and determined a photometric period of 2.36 days together with an orbital inclination of 61.8°. The best-fitting model solution to the light curves suggests a detached configuration. With a primary temperature of T1 = 42 520 K we obtained the temperature of the secondary component as T2 = 41 500 K. The CPD − 51° 8946 system is another known eclipsing binary for which we present a revised photometric period of 1.96 days with an orbital inclination of 58.4°. The system probably has a semi-detached configuration and a mass ratio q = M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34 550 K, we obtain T2 = 21 500 K for the secondary component. The HD 319702 system is a newly discovered eclipsing binary member of the young open cluster NGC 6334. The system shows well-defined eclipses favouring a detached configuration with a period of 2.0 days and an orbital inclination of 67.5°. Combining our photometric result with the primary spectral type O8 III(f) (T1 = 34 000 K) we derive a temperature of T2 = 25 200 K for the secondary component.