Thursday, May 9, 2013

1305.1670 (Kevin B. Stevenson et al.)

Transmission Spectroscopy of the Hot-Jupiter WASP-12b from 0.7 to 5 microns    [PDF]

Kevin B. Stevenson, Jacob L. Bean, Andreas Seifahrt, Jean-Michel Desert, Nikku Madhusudhan, Marcel Bergmann, Laura Kreidberg, Derek Homeier
Since the first report of a potentially non-solar carbon-to-oxygen ratio (C/O) in its dayside atmosphere, the highly-irradiated exoplanet WASP-12b has been under intense scrutiny and the subject of many follow-up observations. Additionally, the recent discovery of a stellar companion ~1 arcsec from WASP-12 has obfuscated interpretation of the observational data. Here we present new ground-based multi-object transmission-spectroscopy observations of WASP-12b that we acquired over two consecutive nights in the red optical with Gemini-N/GMOS. After correcting for the influence of WASP-12's stellar companion, we find that these data rule out a cloud-free, H2 atmosphere with no additional opacity sources. Some of the observed features may be attributed to metal oxides (such as TiO and VO) for an O-rich atmosphere or to metal hydrides (such as TiH) for a C-rich atmosphere. We also reanalyzed NIR transit-spectroscopy observations of WASP-12b from HST/WFC3 and broadband transit photometry from Warm Spitzer. We attribute the broad spectral features in the WFC3 data to either H2O or CH4 and HCN for an O-rich or C-rich atmosphere, respectively. The Spitzer data suggest shallower transit depths than the models predict at infrared wavelengths, albeit at low statistical significance. We conclude that additional high-precision data and spectroscopic measurements of the companion star are required to place definitive constraints on the composition of WASP-12b's atmosphere.
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