DETECTION OF H2O AND EVIDENCE FOR TiO/VO IN AN ULTRA-HOT EXOPLANET ATMOSPHERE
AuthorEvans, Thomas M.
Sing, David K.
Wakeford, H. R.
Ballester, Gilda E.
Gibson, Neale P.
Amundsen, David S.
AffiliationUniv Arizona, Lunar & Planetary Lab
Keywordsplanets and satellites: atmospheres
stars: individual (WASP-121)
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationDETECTION OF H2O AND EVIDENCE FOR TiO/VO IN AN ULTRA-HOT EXOPLANET ATMOSPHERE 2016, 822 (1):L4 The Astrophysical Journal Letters
Rights© 2016. The American Astronomical Society. All rights reserved.
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AbstractWe present a primary transit observation for the ultra-hot (T-eq similar to 2400 K) gas giant expolanet WASP-121b, made using the Hubble Space Telescope Wide Field Camera 3 in spectroscopic mode across the 1.12-1.64 mu m wavelength range. The 1.4 mu m water absorption band is detected at high confidence (5.4 sigma) in the planetary atmosphere. We also reanalyze ground-based photometric light curves taken in the B, r', and z' filters. Significantly deeper transits are measured in these optical bandpasses relative to the near-infrared wavelengths. We conclude that scattering by high-altitude haze alone is unlikely to account for this difference and instead interpret it as evidence for titanium oxide and vanadium oxide absorption. Enhanced opacity is also inferred across the 1.12-1.3 mu m wavelength range, possibly due to iron hydride absorption. If confirmed, WASP-121b will be the first exoplanet with titanium oxide, vanadium oxide, and iron hydride detected in transmission. The latter are important species in M/L dwarfs and their presence is likely to have a significant effect on the overall physics and chemistry of the atmosphere, including the production of a strong thermal inversion.
VersionFinal published version
SponsorsThe authors would like to thank the referee for their prompt and thoughtful review. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-14468. The authors are grateful to the WASP-121 discovery team for generously providing the ground-based photometric light curves. The research leading to these results received funding from the European Research Council under the European Union Seventh Framework Program (FP7/2007-2013) ERC grant agreement no. 336792. H.R.W. acknowledges support by an appointment to the NASA Postdoctoral Program at Goddard Space Flight Center, administered by ORAU and USRA through a contract with NASA. N.P.G. gratefully acknowledges support from the Royal Society in the form of a University Research Fellowship.