A search for solar-like oscillations in the Am star HD 209625^*

¹ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 200D Celestijnenlaan, 3001 Leuven, Belgium e-mail: fabien@ster.kuleuven.be
² Observatoire de Genève, Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland e-mail: yves@deber.ch
³ Institut d'Astrophysique et de Géophysique, Université de Liège, 17 allée du 6 Août, Bât. B5c, 4000 Liège, Belgium e-mail: [eggenberger;leyder]@astro.ulg.ac.be
⁴ Observatoire de Paris-Meudon, GEPI, 5 place Jules Janssen, 92195 Meudon Cedex, France e-mail: frederic.royer@obspm.fr

Received: 23 December 2006
Accepted: 17 April 2007

Abstract

Aims.The goal is to test the structure of hot metallic stars, and in particular the structure of a near-surface convection zone using asteroseismic measurements. Indeed, stellar models including a detailed treatement of the radiative diffusion predict the existence of a near-surface convection zone in order to correctly reproduce the anomalies in surface abundances that are observed in Am stars.

Methods.The Am star HD 209625 was observed with the harps spectrograph mounted on the 3.6-m telescope at the ESO La Silla Observatory (Chile) during 9 nights in August 2005. This observing run allowed us to collect 1243 radial velocity (RV) measurements, with a standard deviation of 1.35 m s^-1.

Results.The power spectrum associated with these RV measurements does not present any excess. Therefore, either the structure of the external layers of this star does not allow excitation of solar-like oscillations, or the amplitudes of the oscillations remain below 20–30 cm s^-1 (depending on their frequency range).