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Volume 371, Number 1, May III 2001
Page(s) 260 - 266
Section Formation and evolution of planetary systems

A&A 371, 260-266 (2001)
DOI: 10.1051/0004-6361:20010406

Search for spectroscopical signatures of transiting HD 209458b's exosphere

C. Moutou1, A. Coustenis2, J. Schneider2, R. St Gilles2, M. Mayor3, D. Queloz3 and A. Kaufer1

1  ESO, Alonso de Cordova 3107, Santiago de Chile
2  Observatoire de Paris Meudon, 92195 Meudon Cedex, France
3  Observatoire de Genève, Switzerland

(Received 13 November 2000 / Accepted 18 January 2001 )

Following recent attempts to detect the exosphere of the extra-solar planet 51 Pegb in the infrared (Coustenis et al. 1997, 1998; Rauer et al. 2000a), we discuss here a search for optical spectroscopic signatures from a gaseous extended envelope (called exosphere) surrounding the planet HD 209458b. This planet has a demonstrated photometric transit (Charbonneau et al. 2000a; Henry et al. 2000), thus offering an increased probability for the spectroscopic detection of such an envelope. Therefore it is the best known candidate for probing the exospheric composition of a giant planet, orbiting a Sun-like star at a short distance. The observations were performed with UVES at the VLT and cover most of the 328-669 nm range. We did not detect HD 209458b's exosphere at a level of 1% , a value close to the predictions. We discuss here the first results obtained and their limitations, as well as future prospective.

Key words: techniques: spectroscopic -- stars: atmosphere -- stars: planetary systems

Offprint request: C. Moutou,

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