SPECTROSCOPY OF THE MASSIVE BINARY IOTA-ORIONIS AT PERIASTRON

Iota Orionis is a massive binary with a very eccentric orbit, which br ings the stars into close proximity at periastron. The resulting tidal deformation of the primary star is expected to create enhanced mass l oss and stimulate stellar oscillations at each periastron. We present the results of a search for these effects in high S/N spectra of the H alpha and He I lambda 6678 profiles of I Ori obtained over 5.5 hr dur ing a single periastron passage. We fit the He I lambda 6678 data usin g previously determined profiles for both components and using the orb ital solution of Stickland et al. (1987) to establish that periastron occurred at HJD 2,450,072.80 +/- 0.03. Measurements of the projected r otational velocities indicate that both stars rotate more slowly than the orbit at periastron. There is weak, residual H alpha emission that moves with the primary's orbital motion and that may be associated wi th the development of an enhanced, focused wind at periastron. However , the He I lambda 6678 line of the primary star is nearly constant in shape over this interval and we find no evidence for tidally induced o scillations.