Large-scale wind structures in OB supergiants: a search for rotationally modulated Hαvariability

Details Large-scale wind structures in OB supergiants: a search for rotationally modulated Hαvariability Large-scale wind structures in OB supergiants: a search for rotationally modulated Hαvariability

2004-03-05

arxiv.org/abs/astro-ph/0403155v1

Mon.Not.Roy.Astron.Soc. 351 (2004) 552

Astronomy and Astrophysics

Astrophysics

18 pages, accepted for publication in MNRAS

Scientific paper

10.1111/j.1365-2966.2004.07799.x

We present the results of a long-term monitoring campaign of the H\alpha line in a sample of bright OB-supergiants (O7.5-B9) that aims at detecting rotationally modulated changes potentially related to the existence of large-scale wind structures. A total of 22 objects were monitor ed during 36 nights spread over 6 months in 2001-2002. Coordinated broad-band photometric observations were also obtained for some targets. Conspicuous evidence for variability in H\alpha is found for the stars displaying a feature contaminated by wind emission. Most changes take place on a daily time-scale, although hourly variations are also occasionally detected. Convincing evidence for a cyclical pattern of variability in H\alpha has been found in 2 stars: HD 14134 and HD 42087 (periodic signals are also detected in other stars, but independent confirmation is required). Rotational modulation is suggested from the similarity between the observed recurrence time-scales (in the range 13-25 days) and estimated periods of stellar rotation. We call attention to the atypical case of HD 14134 which exhibits a clear 12.8-d periodicity both in the photometric and in the spectroscopic data sets. This places this object among a handful of early-type stars where one may observe a clear link between extended wind structures and photospheric disturbances. Further modelling may test the hypothesis that azimuthally-extended wind streams are responsible for the patterns of spectral variability in our target stars.

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