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dc.contributor.authorRackham, Benjamin
dc.contributor.authorEspinoza, Néstor
dc.contributor.authorApai, Dániel
dc.contributor.authorLópez-Morales, M.
dc.contributor.authorJordán, Andrés
dc.contributor.authorOsip, David J.
dc.contributor.authorLewis, Nikole K.
dc.contributor.authorRodler, Florian
dc.contributor.authorFraine, Jonathan D.
dc.contributor.authorMorley, Caroline V.
dc.contributor.authorFortney, Jonathan J.
dc.date.accessioned2017-04-11T18:57:19Z
dc.date.available2017-04-11T18:57:19Z
dc.date.issued2017-01-10
dc.identifier.citationACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE 2017, 834 (2):151 The Astrophysical Journalen
dc.identifier.issn1538-4357
dc.identifier.doi10.1088/1361-6560/aa4f6c
dc.identifier.urihttp://hdl.handle.net/10150/623098
dc.description.abstractGJ. 1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanet 's atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260 angstrom) of GJ. 1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of Rp R-s = 0.1146. 2 x 10(-4) and mean uncertainty of sigma(R-p/R-s) = 8.7 x 10(-4) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanet's limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r = 0.1 mu m and haze-forming efficiency f(haze) = 10% and (2) faculae in the unocculted stellar disk with a temperature contrast Delta T= 354(-46)(+46) K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.
dc.description.sponsorshipNational Science Foundation Graduate Research Fellowship Program [DGE-1143953]; CONICYT-PCHA/Doctorado Nacional; FONDECYT [1130857]; Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]; BASAL [CATA PFB06]; NASA's Science Mission Directorateen
dc.language.isoenen
dc.publisherIOP PUBLISHING LTDen
dc.relation.urlhttp://stacks.iop.org/0004-637X/834/i=2/a=151?key=crossref.56904a0f1962b448d250861d82b60792en
dc.rights© 2017. The American Astronomical Society. All rights reserved.en
dc.subjectmethods: observationalen
dc.subjectplanets and satellites: atmospheresen
dc.subjectplanets and satellites: individual (GJ 1214b)en
dc.subjectstars: activityen
dc.subjecttechniques: spectroscopicen
dc.titleACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHEREen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Steward Observ, Dept Astronen
dc.contributor.departmentUniv Arizona, Lunar & Planetary Laben
dc.identifier.journalThe Astrophysical Journalen
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en
dc.eprint.versionFinal published versionen
refterms.dateFOA2018-09-11T18:31:01Z
html.description.abstractGJ. 1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanet 's atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260 angstrom) of GJ. 1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of Rp R-s = 0.1146. 2 x 10(-4) and mean uncertainty of sigma(R-p/R-s) = 8.7 x 10(-4) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanet's limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r = 0.1 mu m and haze-forming efficiency f(haze) = 10% and (2) faculae in the unocculted stellar disk with a temperature contrast Delta T= 354(-46)(+46) K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.


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