A spectroscopic study of southern (candidate) γ Doradus stars

I. Time series analysis

¹ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium e-mail: peter@oma.be
² Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
³ Observatoire de Genève, 1290 Sauverny, Switzerland
⁴ Department of Astrophysics, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁵ Centre for Astrophysics, University of Central Lancashire, Preston, PR1 2HE, UK
⁶ Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Wien, Austria
⁷ Mercator Telescope, Calle Alvarez de Abreu 70, 38700 Santa Cruz de La Palma, Spain
⁸ Observatoire de la Côte d'Azur, Département Gemini, UMR 6203, 06304 Nice Cedex 4, France
⁹ Laboratoire Univ. d'Astroph. de Nice (LUAN), UMR 6525, Parc Valrose, 06108 Nice Cedex 02, France

Received: 17 June 2005
Accepted: 27 October 2005

Abstract

We present the results of a spectroscopic study of 37 southern (candidate) γ Doradus stars based on échelle spectra. The observed spectra were cross-correlated with the standard template spectrum of an F0-type star for easier detection of binary and intrinsic variations. We identified 15 objects as spectroscopic binaries, including 7 new ones, while another 3 objects are binary suspects. At least 12 objects show composite spectra. We could determine the orbital parameters for 9 binaries, of which 4 turned out to be ellipsoidal variables. For 6 binaries, we estimated the expected time-base of the orbital variations. Clear profile variations were observed for 17 objects, pointing towards stellar pulsation. For 8 of them, we have evidence that the main spectroscopic and photometric periods coincide. Our results, in combination with prior knowledge from the literature, lead to the classification of 10 objects as new bona fide γ Doradus stars, 1 object as a new bona fide δ Scuti star, and 8 objects as constant stars. Finally, we determined the projected rotational velocity by two independent methods. The resulting  values range from 3 to 135 . For the bona fide γ Doradus stars, the majority has  below 60 .