Abstract

P. Mathias¹, E. Chapellier¹, J.-M. Le Contel¹, J.-P. Sareyan¹, Garrido², E. Rodriguez², E. Poretti³, A. Arellano Ferro⁴, L. Alvarez ⁴, L. Parrao⁴ L. Eyer⁵, C. Aerts⁶, W. Weiss⁷, A. Zhou⁸

¹ Observatoire de la Côte d'Azur, Département Fresnel, UMR 6528, F-06304 Nice Cedex 4, France
² Instituto de Astrofisica de Andalucia, Apt. 3044, E-18080 Granada, Spain
³ Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy
⁴ Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F., 04510
⁵ Princeton University Observatory, Princeton, NJ 08544, USA
⁶ Katholieke Universiteit Leuven, Departement Natuurkunde en Sterrenkunde, Celestijnenlaan 200 B, B - 3001 Leuven, Belgium
⁷ Institute for Astronomy, University of Vienna, Tuerkenschanzstrasse 17, 1180 Vienna, Austria
⁸ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China

Asterosismology requires intensive monitoring as well as a large precision in the measures. These objectives will be fulfilled by the COROT mission (http://www.astrsp-mrs.fr/projets/corot/) which will observe

Scuti and Sun-like stars during runs of 150 days. However, up to now, the modes detected in these stars are p-modes, propagating preferentially in the outer layers. It should be valuable to monitor also stars presenting g-modes which propagate deeper. These modes have been detected in a few stars (DA and DB white dwarfs, SPB and

Doradus stars essentially). Among them,

Doradus stars match very well the scientific aspects investigated by COROT, i.e. pulsation in solar-like and classical

Scuti stars. The

Doradus stars, laying in the HRD in between the Sun and the

Scuti stars, constitute a new class of pulsating variables discovered only recently. These objects are thought to exhibit multiperiodic high-order low degree g-mode oscillations with periods in the range of 0.5 - 3 days (see e.g. Kaye et al. 1999, PASP 111, 840). One proposed destabilization mechanism is explained by the modulation of the radiative flux by convection at the base of a deep envelope convection zone (Guzik et al. 2000, ApJ 542, L57). Much effort is currently made to find new members of this group, to constrain their pulsation characteristics and their position in the HRD. On one side, where is the

Doradus stars red border, on the other side where stands the blue border as some

Scuti stars have also been classified as

Doradus stars? Indeed, the number of bona fide members is still low, and show quite a large variety in their observational behaviour (see e.g. http://sirius.saao.ac.za/~gerald/gdorlist.html). For instance, their observational instability strip partly covers that of

Scuti stars, and at least one

Doradus variable also pulsates in

Scuti p-modes (Handler et al., in press). In this case, these "hybrids" are particularly important for asterosismology since both the upper and deeper layers are probed by respectively p- and g-waves. A few stars with surface abundances peculiarities have also been observed to exhibit

Doradus variations, e.g.

Bootis stars (Gray & Kaye 1999, AJ 118, 2993) or Am stars (Gray & Kaye, in preparation). We will present here the first results of an international multisite multitechnique campaign concerning a large sample of

Doradus candidates. In particular, we derived the upper v sin i value, and the variability. This work is at half track, the final objectives being to identifiy at least the main pulsation modes for the maximum number of stars and to select at least one star for a COROT Additional Program.