Velocity variability of semiregular and irregular variables

¹ Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Vienna, Austria
² National Optical Astronomy Observatory (Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.) , 950 N. Cherry Avenue, PO Box 26732, Tucson, Arizona 85726, USA

Corresponding author: T. Lebzelter, lebzelter@astro.univie.ac.at

Received: 17 April 2002
Accepted: 11 July 2002

Abstract

We compare velocities from near infrared lines with center-of-mass velocities for a sample of semiregular and irregular variables to search for indications for a convective blueshift. It is shown that a general blueshift is present but that the light variability is obviously not dominated by convective cells but rather by stellar pulsation. All stars of our sample show a similar shape and amplitude in the velocity variations. Long secondary periods are a common feature in these objects and strongly influence the measured velocity shifts. The star V366 Aql is found to be the first SRV showing line doubling.