A Ground-based Search for Thermal Emission from the Exoplanet TrES-1
Eclipsing planetary systems give us an important window on extrasolar planet atmospheres. By measuring the depth of the secondary eclipse, when the planet moves behind the star, we can estimate the strength of the thermal emission from the day side of the planet. Obtaining a ground‐based detection of one of these eclipses has proven to be a significant challenge, as time‐dependent variations in instrument throughput and atmospheric seeing and absorption overwhelm the small signal of the eclipse at infrared wavelengths. We gathered a series of simultaneous L grism spectra of the transiting planet system TrES‐1 and a nearby comparison star of comparable brightness, allowing us to correct for these effects, in principle. Combining the data from two eclipses, we demonstrate a detection sensitivity of 0.15% in the eclipse depth relative to the stellar flux. This approaches the sensitivity required to detect the planetary emission, which theoretical models predict should lie between 0.05% and 0.1% of the stellar flux in our 2.9–4.3 μm bandpass. We explore the factors that ultimately limit the precision of this technique, and discuss potential avenues for future improvements.
Additional Information© 2007 Astronomical Society of the Pacific. Received 2007 April 19; accepted 2007 May 24; published 2007 June 12. This work is based on observations obtained as part of program GN-2006A-Q-3 at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina). We are grateful to Chad Trujillo and the entire Gemini team for their assistance throughout this process. H. A. K. was supported by a National Science Foundation Graduate Research Fellowship. L. J. R. was supported by a NASA Postdoctoral Fellowship at NASA Goddard.
Accepted Version - 0705.4288.pdf