J/ApJ/745/77ivo://CDS.VizieR/J/ApJ/745/77doi:10.26093/cds/vizier.17450077CDSKopparapu R.K.Kasting J.F.Zahnle K.J.2013-09-04T21:37:19Z2013-08-09T10:59:02ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frastronomical-modelssolar-system-planetsThe hot-Jupiter WASP-12b is a heavily irradiated exoplanet in a short-period orbit around a G0-star with twice the metallicity of the Sun. A recent thermochemical equilibrium analysis based on Spitzer and ground-based infrared observations suggests that the presence of CH_4_ in its atmosphere and the lack of H_2_O features can only be explained if the carbon-to-oxygen ratio in the planet's atmosphere is much greater than the solar ratio ([C]/[O]=0.54). Here, we use a one-dimensional photochemical model to study the effect of disequilibrium chemistry on the observed abundances of H_2_O, CO, CO_2_, and CH_4_ in the WASP-12b atmosphere. We consider two cases: one with solar [C]/[O] and another with [C]/[O]=1.08. The solar case predicts that H_2_ O and CO are more abundant than CO_2_ and CH_4_, as expected, whereas the high [C]/[O] model shows that CO, C_2_H_2_, and HCN are more abundant. This indicates that the extra carbon from the high [C]/[O] model is in hydrocarbon species. H_2_ O photolysis is the dominant disequilibrium mechanism that alters the chemistry at higher altitudes in the solar [C]/[O] case, whereas photodissociation of C_2_H_2_ and HCN is significant in the super-solar case. Furthermore, our analysis indicates that C_2_H_2_ is the major absorber in the atmosphere of WASP-12b and the absorption features detected near 1.6 and 8{mu}m may be arising from C_2_H_2_ rather than CH_4_. The Hubble Space Telescope's WFC3 can resolve this discrepancy, as C_2_H_2_ has absorption between 1.51 and 1.54{mu}m, while CH_4_ does not.2012ApJ...745...77Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/745/77CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/551/A108 : Multi-site obs. of WASP-12 b transit (Maciejewski+, 2013)J/AJ/143/39 : Analysis of hot Jupiters in Kepler Q2 (Coughlin+, 2012)J/A+A/528/A65 : WASP-12b transits (Maciejewski+, 2011)J/ApJ/720/872 : A spectropolarimetric analysis of WASP-12 (Fossati+, 2010)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/745/77https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/745/77http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/745/77https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/745/77https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/745/77http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/745/77GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/ApJ/745/77/table1Reaction list and rate constants (K. Zahnle 2010, private communication) used in this studybRate: exponential factor (2)stat.fit.paramdoubleaRate: temperature exponent (2)stat.fit.paramdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNum[1/166] Reaction number (1)meta.idintR1Reactant 1 (among 31 chemical species)phys.atmol.elementcharR2Reactant 2 (among 31 chemical species)phys.atmol.elementcharR3[M] Reactant 3 (among 31 chemical species)phys.atmol.elementcharP1Product 1 (among 31 chemical species)phys.atmol.elementcharP2Product 2 (among 31 chemical species)phys.atmol.elementcharP3[H/M] Product 3phys.atmol.elementcharKRate: K coefficient (2)stat.fit.paramdoublef_Ref[r-] r-: "reverse of" (2)meta.codecharRefReference (see refs.dat file)meta.ref;pos.framecharJ/ApJ/745/77/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCodeReference codemeta.notecharAutAuthor's name(s)meta.bib.authorcharYearYear of publicationtime.epochintCommTitle and reference of the publicationmeta.notechar