PHOTOMETRIC MONITORING OF O-TYPE STARS

We have conducted a photometric survey of 16 bright O-type stars in order to determine the incidence of low-order non-radial pulsation or other variability among them. For each star, several observations were obtained per night so that periodicities as short as one hour can be detected. Our results show that microvariability with a time-scale of the order of days is present in all the O supergiants and in some dwarfs. Except for zeta Oph, no periodicity characteristic of non-radial pulsation could be found in any of the stars. However, high-order modes would not have been detected. One O-type star is a previously unknown eclipsing binary. In the process of this study, two new B-type eclipsing binaries were discovered.