SEARCH FOR RAYLEIGH SCATTERING IN THE ATMOSPHERE OF GJ1214b

• Main Authors: de Mooij, E. J. W. (Author), Brogi, M. (Author), de Kok, R. J. (Author), Snellen, I. A. G. (Author), Jayawardhana, Ray (Author), Hoekstra, H. (Author), Otten, G. P. P. L. (Author), Bekkers, D. H. (Author), Haffert, S. Y. (Author), van Houdt, J. J. (Author), Croll, Bryce J. (Contributor)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2015-02-03T20:16:50Z.
• Subjects: Article
• Online Access: Get fulltext

We investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the spectrum. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Most observations favor a water-dominated atmosphere with a small scale-height, however, some observations indicate that GJ1214b could have an extended atmosphere with a cloud layer muting the molecular features. In an atmosphere with a large scale-height, Rayleigh scattering at blue wavelengths is likely to cause a measurable increase in the apparent size of the planet toward the blue. We observed the transit of GJ1214b in the B band with the FOcal Reducing Spectrograph at the Very Large Telescope and in the g band with both ACAM on the William Herschel Telescope (WHT) and the Wide Field Camera at the Isaac Newton Telescope (INT). We find a planet-to-star radius ratio in the B band of 0.1162 ± 0.0017, and in the g band 0.1180 ± 0.0009 and 0.1174 ± 0.0017 for the WHT and INT observations, respectively. These optical data do not show significant deviations from previous measurements at longer wavelengths. In fact, a flat transmission spectrum across all wavelengths best describes the combined observations. When atmospheric models are considered, a small scale-height water-dominated model fits the data best.
Natural Sciences and Engineering Research Council of Canada
United States. National Aeronautics and Space Administration (Sagan Fellowship)