THE LINE-PROFILE VARIABLE LAMBDA-SCORPII IS A SPECTROSCOPIC TRIPLE SYSTEM

An analysis of 278 spectra of the line-profile variable lambda Scorpii leads to the following conclusions. lambda Sco is the primary of a bi nary system. The radial-velocity variations have a peak-to-peak amplit ude of similar to 60 km/s and an orbital period of 5.959 days. The orb it is not circular but has an eccentricity of 0.29. The 5(d).959-binar y system probably moves in orbit with another distant, as yet unknown third star. By means of three five-hour time series of high-resolution spectra, the oscillations of the rapidly rotating beta Cephei-type ma in component are investigated. Line-profile variations, which reveal t ravelling subfeatures across the lines, are discovered. lambda Sco is so far one of the very few beta Cephei stars in which such a moving-bu mp phenomenon is detected. Radial-velocity variations are derived from the data and analysed to reveal a main oscillation frequency near 4.6 6 cycles day(-1), and some more candidate frequencies. lambda Sco is a non-radially pulsating beta Cephei star which rotates supersynchronou sly. The characteristics of lambda Sco and the zeta Oph stars are brie fly addressed. Despite the common line-profile behaviour, spectral typ e, and v sin i, we find no evidence of circumstellar material around l ambda Sco.