A Large, Periodic Variation in the Stellar Wind of theta 1 Orionis C

Abstract

A period of 15.4 days, recently discovered by Stahl et al. from intensive monitoring of hydrogen alpha emission in Theta¹ Ori C during 1992-1993, has been found to phase large variations in the C IV lambda lambda 1548, 1551 wind profile of this star previously reported from International Ultraviolet Explorer (IUE) high-resolution data obtained during 1978-1983. These stellar-wind variations are among the largest observed in O stars not known to be components of interacting binaries; the strict periodicity is unique among apparently single O stars and constitutes an important constraint on the unknown origin of the phenomenon.