The spectral variability of HD 192639 and its implications for the star's wind structure^*

¹ Institut d'Astrophysique et de Géophysique, Université de Liège, 5 avenue de Cointe, 4000 Liège, Belgium
² Ritter Astrophysical Research Center, Toledo, OH 43606, USA

G. Rauw

Received: 7 August 2000
Accepted: 9 November 2000

Abstract

We report the analysis of an extensive set of spectroscopic data of the O(f) supergiant HD 192639. A Fourier analysis of our time-series reveals a recurrent variability with a "period"of roughly 4.8 days which is most prominent in the absorption components of the He ii λ 4686 and Hα P-Cygni profiles. The same periodicity is also detected in the blue wing of several absorption lines (e.g. Hβ). The variations of the absorption components correspond most probably to a cyclical modulation of the amount of stellar wind material along the line of sight towards the star. The 4.8-day period affects also the morphology of the double-peaked He ii λ 4686 and Hα emission components, although these emission components display also variations on other (mainly longer) time scales. The most likely explanation for the 4.8-day modulation is that this cycle reflects the stellar rotational period (or half this period). We find that the most important observational properties can be explained -at least qualitatively -by a corotating interaction region or a tilted confined corotating wind.