ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE
Osip, David J.
Lewis, Nikole K.
Fraine, Jonathan D.
Morley, Caroline V.
Fortney, Jonathan J.
AffiliationUniv Arizona, Steward Observ, Dept Astron
Univ Arizona, Lunar & Planetary Lab
planets and satellites: atmospheres
planets and satellites: individual (GJ 1214b)
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE 2017, 834 (2):151 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2017. The American Astronomical Society. All rights reserved.
Collection InformationThis 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 firstname.lastname@example.org.
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.
VersionFinal published version
SponsorsNational Science Foundation Graduate Research Fellowship Program [DGE-1143953]; CONICYT-PCHA/Doctorado Nacional; FONDECYT ; Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]; BASAL [CATA PFB06]; NASA's Science Mission Directorate