Long period variables in the globular cluster 47 Tuc: Radial velocity variations

¹ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: lebzelter@astro.univie.ac.at
² Research School for Astronomy & Astrophysics, Mount Stromlo Observatory, Weston, ACT 2611, Australia
³ National Optical Astronomy Observatory (Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.) , PO Box 26732, Tucson, AZ 85726, USA
⁴ Center of Excellence in Information Systems, Tennessee State University, Nashville, TN 37203-3401, USA

Received: 29 January 2004
Accepted: 31 October 2004

Abstract

We present near infrared velocity curves for 12 long period variables (LPVs) in the globular cluster 47 Tuc (NGC 104). New light curves are also presented for these variables. Results are compared with the period-luminosity sequences occupied by the LPVs in the LMC. Sequence C variables (fundamental mode pulsators) have larger velocity amplitudes than sequence B variables (first overtone pulsators). We show that, at similar luminosities, higher mass loss rates are associated with larger pulsation amplitudes. One variable (V18) does not fit the normal period luminosity sequences and it has an unusually large amount of circumstellar dust, suggesting that it has recently undergone a thermal pulse on the AGB. Finally, we report the discovery of three new long period variable stars in the cluster core, all previously found to have a large infrared excess.