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T.M. Brown (NCAR), R.P. Butler (CIW), D. Charbonneau (NCAR,CfA), R.W. Noyes, D. Sasselov (CfA), K.G. Libbrecht (CalTech), G.W. Marcy (U.C. Berkeley), S. Seager (IAS), S.S. Vogt (U.C. Santa Cruz)
Transiting extrasolar giant planets such as HD209458b should impress a spectroscopic signature on the light that is transmitted through the outer parts of their atmospheres. Theory suggests that the depths of absorption features resulting from this effect may be as large as about 10-3 of the parent star's continuum intensity. Such spectral features could provide important diagnostics concerning the composition and physical state of the planetary atmosphere. Accordingly, we have obtained low-noise spectra of HD209458 during two transits of its planet, once in visible light using the HIRES spectrograph at the Keck I telescope, and once in the near infrared using the NIRSPEC spectrograph at Keck II. We describe the methods employed and the results of searches for spectral signatures of neutral atomic sodium, carbon monoxide, and other atomic and molecular species.