The eclipsing double-lined binaries V883 Cen and Mus

Abstract

We derive the orbital period and monitor in detail the eclipses of two deep-southern double-lined eclipsing binaries of considerable interest. We present new uvby photometry over more than 100 nights for V883 Cen, scan for the first time the eclipses of η Mus and analyse the data for these two systems together with earlier published photometry. We also add information from high-dispersion spectra. V883 Cen consists of two sharp-lined, mid-B-type stars in an orbit of 35.44733 d. The slower rotating component, Prot= 55.215 d, is a chemically peculiar star of the type He-weak SrTi that is partially eclipsed by its slightly more massive companion. Owing to the high eccentricity of the orbit and its orientation, only one eclipse occurs. The orbital period of η Mus is 57.5 h, rather than the 20 d quoted up to the present in the literature. That close binary, consisting of two late-B-type stars, shows identical partial eclipses. Interest in the close binary is triggered by the pre-main-sequence companion at 2.7 arcsec. HD 118978, one of the comparison stars used for V883 Cen, is identified as a new variable. This fast-rotating B9 (sub)giant belongs presumably to the class of slowly pulsating B-type stars.