Abstract
An observational description is presented of the time-dependent behaviour of Discrete Absorption Components (DACs) in ultraviolet spectra of O-type stars. DACs represent the strongest manifestation of stellar-wind variability, a characteristic property of radiation-driven winds. Wind variability sets in already close to the star, as is evidenced by the low-velocity variations in several subordinate ultraviolet and optical lines. The observed characteristic timescale of the variability strongly suggests that stellar rotation plays a dominant role. We discuss the DAC behaviour in terms of a model in which (localized) surface magnetic field regions impose an additional boundary condition at the base of the stellar wind, which may give rise to the observed large-scale structures.
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Kaper, L., Henrichs, H.F. Wind variability in O-type stars. Astrophys Space Sci 221, 115–133 (1994). https://doi.org/10.1007/BF01091147
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DOI: https://doi.org/10.1007/BF01091147