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Asymmetry of metallic spectral lines in Cepheids

Published online by Cambridge University Press:  15 February 2018

Michael Albrow  and
P.L. Cottrel
Michael Albrow
Affiliation:
Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
P.L. Cottrel
Affiliation:
Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand

Abstract

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A program of high resolution spectroscopic observations of Cepheids has been carried out at Mt John University Observatory for several years. Radial velocities and asymmetries have been measured for selected metallic lines using the method of Wallerstein et al (1992).

The line profiles show the largest asymmetry at phases of maximum inward velocity. The asymmetry at phases of maximum outward velocity is smaller and sometimes in the same direction as for the inward velocity maxima. Enhanced asymmetry is also noticed at phases where the bump appears on the radial velocity curve.

To date our models are unable to predict such behaviour. It is important that a satisfactory explaination for these observations be found so that the accuracy of Baade-Wesselink radius solutions for such stars can be assessed.

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 375
Copyright
Copyright © Cambridge University Press 1993

References

Wallerstein, G., Jacobsen, T., Cottrell, P.L., Clark, M. & Albrow, M., 1992, M.N.R.A.S. in press.Google Scholar