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[11.21] The Search for H₃⁺ Towards HD209458

J. Haywood, E. Gibb, T. Rettig (University of Notre Dame), S. Brittain (NOAO), C. Kulesa (University of Arizona)

We present initial results of a search for H₃⁺ in the extended atmosphere towards the giant exoplanet orbiting HD 209458. The observations were taken during 3 transits on June 8, June 15, and July 31, 2004 using NIRSPEC at the Keck II Observatory atop Mauna Kea, Hawaii. NIRSPEC provides high sensitivity and spectral resolution (R ~2.5 \times 10⁴). Unfortunately, the instrument filter wheel was stuck in the K-prime position during our June observations, necessitating a search for the 2 \nu₂² arrow 0 Q(1,0) and Q(3,0) transitions of H₃⁺ lines at 2.04 \mum rather than the stronger \nu₂ arrow 0 R(1,1)^u and R(1,0) transitions near 3.68 \mum. In addition, we also made simultaneous observations of HD 209458 with CSHELL on June 15, which also provides high resolution (R ~2 \times 10⁴). Data analysis is complicated by the fact that the Doppler shift of the planet as it orbits the star changes dramatically over the course of the transit, requiring very careful stacking of each data frame. We discuss our procedures, initial results, and plans for future searches of atmospheric constituents of exoplanets.

We would like to acknowledge support from the National Science Foundation AST 02-05881 and NASA Keck through the Michelson Science Center.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.