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Published January 10, 2009 | Published
Journal Article Open

Molecular Signatures in the Near-Infrared Dayside Spectrum of HD 189733b


We have measured the dayside spectrum of HD 189733b between 1.5 and 2.5 μm using the NICMOS instrument on the Hubble Space Telescope. The emergent spectrum contains significant modulation, which we attribute to the presence of molecular bands seen in absorption. We find that water (H2O), carbon monoxide (CO), and carbon dioxide (CO2) are needed to explain the observations, and we are able to estimate the mixing ratios for these molecules. We also find temperature decreases with altitude in the ~0.01 < P< ~1 bar region of the dayside near-infrared photosphere and set an upper limit to the dayside abundance of methane (CH4) at these pressures.

Additional Information

© 2009 The American Astronomical Society. Received 2008 September 7, accepted for publication 2008 October 31. Published 2008 December 19. Print publication: Issue 2 (2009 January 10). We thank Tommy Wiklind, Nor Prizkal, and other members of the Space Telescope Science Institute staff for extensive assistance in planning the observations and for providing advice about ways in which the observations could be optimized. We also thank Jonathan Fortney for helpful recommendations on improving the presentation of this material. G.T. was supported by the UK Sciences & Technology Facilities Council. A portion of the research described in this paper was carried out at the Jet Propulsion Laboratory, under a contact with the National Aeronautics and Space Administration.

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