Journal
ASTRONOMICAL JOURNAL
Volume 147, Issue 6, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-6256/147/6/161
Keywords
planetary systems; stars: individual (WASP-12); techniques: spectroscopic
Categories
Funding
- NASA [NNX13AJ16G]
- Alfred P. Sloan Foundation
- NASA through the Sagan Exoplanet Fellowship program
- Yale Center for Astronomy and Astrophysics (YCAA) through the YCAA postdoctoral prize fellowship
- National Science Foundation Graduate Research Fellowship Program
- European Research Council under the European Community's Seventh Framework Programme (FP7) [247060]
- NASA [472434, NNX13AJ16G] Funding Source: Federal RePORTER
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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 stellar binary companions similar to 1 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 companions, we find that these data rule out a cloud-free H-2 atmosphere with no additional opacity sources. We detect features in the transmission spectrum that 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. A multi-instrument, broad-wavelength analysis ofWASP-12b suggests that the transmission spectrum is well approximated by a simple Rayleigh scattering model with a planet terminator temperature of 1870 +/- 130 K. We conclude that additional high-precision data and isolated spectroscopic measurements of the companion stars are required to place definitive constraints on the composition of WASP-12b's atmosphere.
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