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The puzzling chemical composition of GJ 436b's atmosphere: influence of tidal heating on the chemistry

hal.structure.identifierSSE 2014
dc.contributor.authorAGÚNDEZ, M.
hal.structure.identifierLaboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
hal.structure.identifierObservatoire aquitain des sciences de l'univers [OASU]
hal.structure.identifierUniversité Sciences et Technologies - Bordeaux 1 [UB]
dc.contributor.authorVENOT, O.
hal.structure.identifierSSE 2014
dc.contributor.authorSELSIS, Franck
dc.contributor.authorIRO, N.
dc.date.created2013-12-10
dc.date.issued2014
dc.identifier.issn0004-637X
dc.description.abstractEnThe dissipation of the tidal energy deposited on eccentric planets may induce a heating of the planet that affects its atmospheric thermal structure. Here we study the influence of tidal heating on the atmospheric composition of the eccentric (e = 0.16) "hot Neptune" GJ 436b, for which inconclusive chemical abundances are retrieved from multiwavelength photometric observations carried out during primary transit and secondary eclipse. We build up a one-dimensional model of GJ 436b's atmosphere in the vertical direction and compute the pressure-temperature and molecular abundances profiles for various plausible internal temperatures of the planet (up to 560 K) and metallicities (from solar to 100 times solar), using a radiative-convective model and a chemical model which includes thermochemical kinetics, vertical mixing, and photochemistry. We find that the CO/CH4 abundance ratio increases with metallicity and tidal heating, and ranges from 1/20 to 1000 within the ranges of metallicity and internal temperature explored. Water vapour locks most of the oxygen and reaches a very high abundance, whatever the metallicity and internal temperature of the planet. The CO2/H2O abundance ratio increases dramatically with metallicity, and takes values between 1e-5-1e-4 with solar elemental abundances and 0.1 for a metallicity 100 times solar. None of the atmospheric models based on solid physical and chemical grounds provide a fully satisfactory agreement with available observational data, although the comparison of calculated spectra and observations seem to point to models with a high metallicity and efficient tidal heating, in which high CO/CH4 abundance ratios and warm temperatures in the dayside atmosphere are favoured.
dc.language.isoen
dc.publisherAmerican Astronomical Society
dc.title.enThe puzzling chemical composition of GJ 436b's atmosphere: influence of tidal heating on the chemistry
dc.typeArticle de revue
dc.identifier.doi10.1088/0004-637X/781/2/68
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]/Planétologie et astrophysique de la terre [astro-ph.EP]
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Planétologie et astrophysique de la terre [astro-ph.EP]
dc.identifier.arxiv1312.3007
bordeaux.journalThe Astrophysical Journal
bordeaux.pageid. 68
bordeaux.volume781
bordeaux.issue2
bordeaux.peerReviewedoui
hal.identifierhal-00949326
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00949326v1
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