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Astron. Astrophys. 350, 553-565 (1999)


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The incidence of nonradial pulsation in the [FORMULA] Bootis stars *

D.A. Bohlender **  1, J.-F. Gonzalez ***  2,3 and J.M. Matthews***  4

1 National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC, Canada V8X 4M6 (David.Bohlender@hia.nrc.ca)
2 European Southern Observatory, Casilla 19001, Santiago 19, Chile (jfgonzal@eso.org)
3 Centre de Recherche Astronomique de Lyon (CNRS-UMR 5574), Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cédex 07, France (Jean-Francois.Gonzalez@ens-lyon.fr)
4 Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z4 Canada (matthews@astro.ubc.ca)

Received 30 November 1998 / Accepted 29 March 1999

Abstract

We have conducted a high-resolution, high signal-to-noise spectroscopic survey of the members of the peculiar [FORMULA] Boo stars accessible from the Canada-France-Hawaii Telescope to investigate the incidence of high-degree nonradial pulsation (NRP) in these metal-deficient stars. Of 16 objects observed more than once, 9 show conclusive evidence of such NRP, which confirms that pulsational instability is a common phenomenon in the [FORMULA] Boo class.

The widespread presence of NRP in the [FORMULA] Boo stars indirectly supports the accretion/diffusion scenario for the formation of these objects, but unfortunately does not rule out other possible causes for the phenomena. However, extensive time-series photometry and spectroscopy of several particularly interesting pulsating members of the class noted here should provide asteroseismologists with the eigenfrequency data needed to resolve the current debate concerning the evolutionary status, and hence, the origin of these peculiar stars. From our survey, we also identify a set of four stars, including [FORMULA] Boo itself, with similar fundamental parameters but remarkably different pulsation characteristic. These stars may offer vital clues as to the physical excitation of [FORMULA] Boo pulsations.

Key words: stars: oscillations – stars: peculiar – stars: variables: general

* Figs. 2-5, 7-10 are only available in the electronic version.
** Formerly at: Canada-France-Hawaii Telescope Corporation, PO Box 1597, Kamuela, HI 96743, USA
*** Visiting Astronomer, Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Send offprint requests to: D.A. Bohlender

© European Southern Observatory (ESO) 1999

Online publication: October 4, 1999

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