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Ultraviolet Studies of Cepheids

Published online by Cambridge University Press:  15 February 2018

Erika Böhm-Vitense
Erika Böhm-Vitense*
Affiliation:
University of Washington, Seattle, Washington Guest observer with the International Ultraviolet Explorer (IUE) Satellite

Abstract

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We discuss whether with new evolutionary tracks we still have a problem fitting the Cepheids and their evolved companions on the appropriate evolutionary tracks. We find that with the Bertelli et al. tracks with convective overshoot by one pressure scale hight the problem is essentially removed though somewhat more mixing would give still better fits.

Using results of recent nonlinear hydrodynamic calculations by Morgan we find that we also have no problem matching the observed pulsation periods of the Cepheids with those expected from their new evolutionary masses, provided that Cepheids with periods less than 9 days are overtone pulsators.

We investigate possible mass loss of Cepheids from UV studies of the companion spectrum of S Mus and from the ultraviolet spectra of the long period Cepheid Carinae. For S Mus with a period of 9.6 days we derive an upper limit for the mass loss of M < 10-9 M⊙, if a standard velocity law is assumed for the wind. For Carinae with a period of 35.5 days we find a probable mass loss of M ∼ 10-5±2 M⊙.

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 387 - 395
Copyright
Copyright © Cambridge University Press 1993

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