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On signatures of clouds in exoplanetary transit spectra

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cam.issuedOnline2017-07-21
cam.orpheus.successWed Apr 01 08:15:44 BST 2020 - The item has an open VoR version.
dc.contributor.authorPinhas, A
dc.contributor.authorMadhusudhan, N
dc.contributor.orcidNikku, Madhusudhan [0000-0002-4869-000X]
dc.date.accessioned2018-05-21T12:42:01Z
dc.date.available2018-05-21T12:42:01Z
dc.date.issued2017-11
dc.description.abstract© 2017 The Authors. Transmission spectra of exoplanetary atmospheres have been used to infer the presence of clouds/hazes. Such inferences are typically based on spectral slopes in the optical deviant from gaseous Rayleigh scattering or low-amplitude spectral features in the infrared. We investigate three observable metrics that could allow constraints on cloud properties from transmission spectra, namely the optical slope, the uniformity of this slope and condensate features in the infrared. We derive these metrics using model transmission spectra considering Mie extinction from a wide range of condensate species, particle sizes and scaleheights. First, we investigate possible degeneracies among the cloud properties for an observed slope. We find, for example, that spectra with very steep optical slopes suggest sulphide clouds (e.g. MnS, ZnS, Na2S) in the atmospheres. Secondly, (non)uniformities in optical slopes provide additional constraints on cloud properties, e.g. MnS, ZnS, TiO2 and Fe2O3 have significantly non-uniform slopes. Thirdly, infrared spectra provide an additional powerful probe into cloud properties, with SiO2, Fe2O3, Mg2SiO4 and MgSiO3 bearing strong infrared features observablewith JamesWebb Space Telescope. We investigate observed spectra of eight hot Jupiters and discuss their implications. In particular, no single or composite condensate species considered here conforms to the steep and non-uniform optical slope observed for HD 189733b. Our work highlights the importance of the three above metrics to investigate cloud properties in exoplanetary atmospheres using high-precision transmission spectra and detailed cloud models. We make our Mie scattering data for condensates publicly available to the community.
dc.identifier.doi10.17863/CAM.23300
dc.identifier.eissn1365-2966
dc.identifier.issn0035-8711
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/276019
dc.language.isoeng
dc.publisherOxford University Press (OUP)
dc.publisher.urlhttp://dx.doi.org/10.1093/mnras/stx1849
dc.subjectradiative transfer
dc.subjectscattering
dc.subjectplanets and satellites: atmospheres
dc.subjectplanets and satellites: composition
dc.subjectplanetary systems
dc.titleOn signatures of clouds in exoplanetary transit spectra
dc.typeArticle
dcterms.dateAccepted2017-07-19
prism.endingPage4373
prism.issueIdentifier4
prism.publicationDate2017
prism.publicationNameMonthly Notices of the Royal Astronomical Society
prism.startingPage4355
prism.volume471
pubs.funder-project-idScience and Technology Facilities Council (ST/N000927/1)
rioxxterms.licenseref.startdate2017-11
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserved
rioxxterms.typeJournal Article/Review
rioxxterms.versionVoR
rioxxterms.versionofrecord10.1093/MNRAS/STX1849

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