EDP Sciences
Free access
Volume 366, Number 2, February I 2001
Page(s) 585 - 597
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000106

A&A 366, 585-597 (2001)
DOI: 10.1051/0004-6361:20000106

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

G. Rauw1, N. D. Morrison2, J.-M. Vreux1, E. Gosset1 and C. L. Mulliss2

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

(Received 7 August 2000 / Accepted 9 November 2000)

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 $\lambda$ 4686 and H$\alpha$ P-Cygni profiles. The same periodicity is also detected in the blue wing of several absorption lines (e.g. H$\beta$). 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 $\lambda$ 4686 and H$\alpha$ 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.

Key words: line: profiles -- stars: early-type -- stars: mass loss -- stars: individual: HD 192639 -- stars: variables: general

Offprint request: G. Rauw

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