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NonRadial Pulsations and the Be Phenomenon
Published online by Cambridge University Press: 23 September 2016
Abstract
Over the last three years I have obtained about 2000 spectra of a sample of 25 rapidly rotating Bn and Be stars. All but two of the program stars show obvious line-profile variations due to non-radial oscillations. The non-emission stars are each pulsating in one or two short-period high-degree (l = 4 to 10) modes, while the Be stars are in all cases pulsating in a long-period % = 2 mode, and often in a short-period high-Z mode as well. The amplitude of the pulsations in several stars (λ Eri, o And, ζ 0ph, and 2 Vul) is correlated with the occurrence of Be outbursts. The amplitude of the pulsations is largest before the outbursts, declines slowly during the emission phases to a fraction of its previous amplitude, and then slowly recovers to its previous amplitude, a few months before the onset of the next outburst. The correspondence between the presence of a long-period % = 2 mode and Ha emission in rapidly rotating B stars strongly suggests that non-radial pulsation and rapid rotation are the essential components which enable single early B stars to become Be stars. The time scale between Be outbursts probably reflects the relaxation oscillation cycle of the I = 2 mode excitation and damping.
- Type
- IV. Models
- Information
- International Astronomical Union Colloquium , Volume 92: Physics of Be Stars , August 1987 , pp. 463
- Copyright
- Copyright © Cambridge University Press 1987