Extrasolar planets and brown dwarfs around A-F type stars

I. Performances of radial velocity measurements, first analyses of variations

¹ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, Université Joseph Fourier, BP 53, 38041 Grenoble, France e-mail: Franck.Galland@obs.ujf-grenoble.fr
² Observatoire de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland

Received: 25 February 2005
Accepted: 23 August 2005

Abstract

We present the performances of a radial velocity measurement method that we developed for A-F type stars. These perfomances are evaluated through an extensive set of simulations, together with actual radial velocity observations of such stars using the ELODIE and HARPS spectrographs. We report the case of stars constant in radial velocity, the example of a binary detection on HD 48097 (an A2V star, with equal to 90 km s) and a confirmation of the existence of a 3.9 M_Jup planet orbiting around HD 120136 (Tau Boo). The instability strip problem is also discussed. We show that with this method, it is in principle possible to detect planets and brown dwarfs around A-F type stars, thus allowing further study of the impact of stellar masses on planetary system formation over a wider range of stellar masses than is currently done.