The data analysis of HD209458 Ly-alpha transit occultation

Désert, J. -M.; Vidal-Madjar, A.; Étangs, A. Lecavelier des; Hébrard, G.; Ballester, G.; Ferlet, R.; Mayor, M.

The data analysis of HD209458 Ly-alpha transit occultation

Authors

Désert, J. -M.

Vidal-Madjar, A.

Étangs, A. Lecavelier des

Description

Using STIS - HST observations, we have detected an extended upper atmosphere in the extrasolar planet HD209458b . The spectra show an absorption of (15+/-4)% of the stellar Ly-alpha emission line during the planetary transit in front of the star. This is interpreted as the signature of HI evaporation taking place around the planet within an extended upper atmosphere (Vidal-Madjar et al. 2003). We present the data analysis of these observations. A particular attention is paid to the background correction and the airglow subtraction.
To be published in the proceedings of the XIXth IAP Colloquium "Extrasolar Planets, Today and Tomorrow", 2 pages