Letter to the Editor

ELODIE metallicity-biased search for transiting Hot Jupiters

II. A very hot Jupiter transiting the bright K star HD 189733

¹ Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, 13013 Marseille, France e-mail: Francois.Bouchy@oamp.fr
² Observatoire de Haute-Provence, 04870 St Michel l'Observatoire, France
³ Observatoire de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
⁴ Lisbon Observatory, Tapada da Ajuda, 1349-018 Lisboa, Portugal
⁵ Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel

Received: 29 September 2005
Accepted: 14 October 2005

Abstract

Context.Among the 160 known exoplanets, mainly detected in large radial-velocity surveys, only 8 have a characterization of their actual mass and radius thanks to the two complementary methods of detection: radial velocities and photometric transit.

Aims.We started in March 2004 an exoplanet-search programme biased toward high-metallicity stars which are more frequently host extra-solar planets. This survey aims to detect close-in giant planets, which are most likely to transit their host star.

Methods.For this programme, high-precision radial velocities are measured with the ELODIE fiber-fed spectrograph on the 1.93-m telescope, and high-precision photometry is obtained with the CCD Camera on the 1.20-m telescope, both at the Haute-Provence Observatory.

Results.We report here the discovery of a new transiting hot Jupiter orbiting the star HD 189733. The planetary nature of this object is confirmed by the observation of both the spectroscopic and photometric transits. The exoplanet HD 189733 b, with an orbital period of 2.219 days, has one of the shortest orbital periods detected by radial velocities, and presents the largest photometric depth in the light curve (%) observed to date. We estimate for the planet a mass of  M_J and a radius of  R_J. Considering that HD 189733 has the same visual magnitude as the well known exoplanet host star HD 209458, further ground-based and space-based follow-up observations are very promising and will permit a characterization of the atmosphere and exosphere of this giant exoplanet.