Program: GN-2012B-Q-16

Transmission spectroscopy is a powerful probe of the atmospheres of transiting extrasolar planets, and has recently become accessible from the ground following the discovery of transiting planets with nearby, bright, comparison stars. Recently, we observed a transit of WASP-29 with GMOS using the multi-object spectrograph in order to perform differential spectro-photometry, that is simultaneously observe the target star and several comparison stars that can be used to correct for changing atmospheric transmission, and produce high precision transit light curves at multiple wavelengths. WASP-29 was in part a test case for the use of GMOS to perform such observations. Analysis of the WASP-29 data has shown great promise, and we request time to observe several more transiting systems that we expect to have a large, detectable signal. We will observe two transits of HAT-P-32 and one of HAT-P-33 using the R400 grism, providing coverage from ~525-925 nm. These planets have large atmospheric scale heights, both being highly inflated hot Jupiters, enabling the search for atomic and molecular species in their atmospheres. Furthermore, our observations will demonstrate that Gemini/GMOS can play a key role in transmission spectroscopy.