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dc.contributor.authorLecavelier des Etangs, A.
dc.contributor.authorEhrenreich, D.
dc.contributor.authorVidal-Madjar, A.
dc.contributor.authorBallester, G.
dc.contributor.authorDesert, J.-M.
dc.contributor.authorFerlet, R.
dc.contributor.authorHebrard, G.
dc.contributor.authorSing, David K.
dc.contributor.authorTchakoumegni, K.-O.
dc.contributor.authorUdry, S.
dc.date.accessioned2014-12-17T15:16:25Z
dc.date.issued2010
dc.description.abstractWe observed three transits of the extrasolar planet HD 189733b in H i Lyman-α and in a few other lines in the ultraviolet with HST/ACS, in the search for atmospheric signatures. We detect a transit signature in the Lyman-α light curve with a transit depth of 5.05 ± 0.75%. This depth exceeds the occultation depth produced by the planetary disk alone at the 3.5σ level (statistical). Other stellar emission lines are less bright, and, taken individually, they do not show the transit signature, while the whole spectra redward of the Lyman-α line has enough photons to show a transit signature consistent with the absorption by the planetary disk alone. The transit depth's upper limits in the emission lines are 11.1% for O i λ1305 Å and 5.5% for C ii λ1335 Å lines.
The presence of an extended exosphere of atomic hydrogen around HD 189733b producing 5% absorption of the full unresolved Lyman-α line flux shows that the planet is losing gas. The Lyman-α light curve is well-fitted by a numerical simulation of escaping hydrogen in which the planetary atoms are pushed by the stellar radiation pressure. We constrain the escape rate of atomic hydrogen to be between 109 and 1011 g s-1 and the ionizing extreme UV flux between 2 and 40 times the solar value (1-σ), with higher escape rates corresponding to larger EUV flux. The best fit is obtained for dM/dt = 1010 g s-1 and an EUV flux FEUV = 20 times the solar value. HD 189733b is the second extrasolar planet for which atmospheric evaporation has been detected.en_GB
dc.description.sponsorshipAgence Nationale pour la Rechercheen_GB
dc.description.sponsorshipCNES (Centre National d'Études Spatiales)en_GB
dc.description.sponsorshipSTScIen_GB
dc.identifier.citationVol. 514, article A72en_GB
dc.identifier.doi10.1051/0004-6361/200913347
dc.identifier.grantnumberNT05-4_44463en_GB
dc.identifier.grantnumberHST-GO-10869.01-Aen_GB
dc.identifier.urihttp://hdl.handle.net/10871/16083
dc.language.isoenen_GB
dc.publisherEDP Sciences for European Southern Observatory (ESO)en_GB
dc.relation.urlhttp://dx.doi.org/10.1051/0004-6361/200913347en_GB
dc.subjectplanetary systemsen_GB
dc.subjectstars: individual: HD 189733en_GB
dc.titleEvaporation of the planet HD 189733b observed in H I Lyman-αen_GB
dc.typeArticleen_GB
dc.date.available2014-12-17T15:16:25Z
dc.identifier.issn0004-6361
dc.descriptionCopyright © ESO, 2010en_GB
dc.identifier.eissn1432-0746
dc.identifier.journalAstronomy and Astrophysicsen_GB


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