NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST /WFC3 SPECTROSCOPY
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Author
Line, Michael R.
Stevenson, K. B.

Bean, Jacob L.

Desert, Jean-Michel

Fortney, Jonathan J.

Kreidberg, Laura

Madhusudhan, Nikku
Showman, Adam P.
Diamond-Lowe, Hannah
Affiliation
Univ Arizona, Dept Planetary SciUniv Arizona, Lunar & Planetary Lab
Issue Date
2016-12-02Keywords
methods: statisticalplanets and satellites: atmospheres
planets and satellites: composition
planets and satellites: gaseous planets
planets and satellites: individual (HD 209458b)
techniques: spectroscopic
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NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST /WFC3 SPECTROSCOPY 2016, 152 (6):203 The Astronomical JournalJournal
The Astronomical JournalRights
© 2016. The American Astronomical Society. All rights reserved.Collection Information
This 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.Abstract
The nature of the thermal structure of hot Jupiter atmospheres is one of the key questions raised by the characterization of transiting exoplanets over the past decade. There have been claims that many hot Jupiters exhibit atmospheric thermal inversions. However, these claims have been based on broadband photometry rather than the unambiguous identification of emission features with spectroscopy, and the chemical species that could cause the thermal inversions by absorbing stellar irradiation at high altitudes have not been identified despite extensive theoretical and observational effort. Here we present high-precision Hubble Space Telescope WFC3 observations of the dayside thermal emission spectrum of the hot Jupiter HD 209458b, which was the first exoplanet suggested to have a thermal inversion. In contrast to previous results for this planet, our observations detect water in absorption at 6.2 sigma confidence. When combined with Spitzer photometry, the data are indicative of a monotonically decreasing temperature with pressure over the range of 1-0.001 bars at 7.7 sigma confidence. We test the robustness of our results by exploring a variety of model assumptions, including the temperature profile parameterization, presence of a cloud, and choice of Spitzer data reduction. We also introduce a new analysis method to determine the elemental abundances from the spectrally retrieved mixing ratios with thermochemical self-consistency and find plausible abundances consistent with solar metallicity (0.06-10 x solar) and carbon-to oxygen ratios less than unity. This work suggests that high-precision spectrophotometric results are required to robustly infer thermal structures and compositions of extrasolar planet atmospheres and to perform comparative exoplanetology.ISSN
1538-3881Version
Final published versionSponsors
GO Treasury Program [13467]; NASA [NAS 5-26555]; David and Lucile Packard Foundation; NASA - Space Telescope Science Institute [51362]; NASA Exoplanet Science Institute Sagan Postdoctoral FellowshipAdditional Links
http://stacks.iop.org/1538-3881/152/i=6/a=203?key=crossref.50d2baf2b47b33096ce51b57d27186dfae974a485f413a2113503eed53cd6c53
10.3847/0004-6256/152/6/203