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Astron. Astrophys. 361, 167-174 (2000)

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A comparison of light and velocity variations in semiregular variables

T. Lebzelter 1, L.L. Kiss 2 and K.H. Hinkle 3

1 Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Vienna, Austria
2 Department of Experimental Physics and Astronomical Observatory, University of Szeged, Hungary
3 Kitt Peak National Observatory, National Optical Astronomy Observatory *, 950 N. Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, USA

Received 22 November 1999 / Accepted 15 June 2000

Abstract

NIR velocity variations are compared with simultaneous visual light curves for a sample of late-type semiregular variables (SRV). Precise radial velocity measurements are also presented for the SRV V450 Aql. Our aim is to investigate the nature of the irregular light changes found in these variables.

Light and velocity variations are correlated in all stars of our sample. Based on these results we discuss several possibilities to explain the observed behavior. We find that pulsation is responsible for large amplitude variations. In a recent paper Lebzelter (1999) invoked large convective cells to understand observed velocity variations. This possibility is discussed with respect to the observed correlation between light and velocity changes. In the light of these results we investigate the origin of the semiregular variations.

Key words: stars: variables: general – stars: late-type – stars: AGB and post-AGB – stars: atmospheres

* Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation

Send offprint requests to: T. Lebzelter (lebzelter@astro.univie.ac.at)

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© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000
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