Photometry and spectroscopy of the eclipsing P Cygni star R 81 in theLarge Magellanic Cloud.

Abstract

IUE high resolution data of the LMC P Cyg star R 81 confirm that the wind characteristics of R 81 and P Cyg are very similar. Photometric monitoring from 1982 to 1986 revealed several brightness minima with a period of 74.59 days. It is concluded that R 81 is an eclipsing binary with this period. From the photometry and the period, a preliminary mass of about 33 solar masses is derived. Interestingly, the scatter around the mean light curve is only about 0.05 mag, i.e., considerably less than the variations usually quoted for P Cyg stars. Since the period of R 81 has been found only after extensive monitoring with high precision within Sterken's (1983) long-term photometry of variables program, this finding may imply that irregular variations reported for P Cyg stars on the basis of less complete data sets may in fact be due to periodic variations.