SEARCH FOR RAYLEIGH SCATTERING IN THE ATMOSPHERE OF GJ1214b

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,...

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Bibliographic Details
Published in:The Astrophysical journal 2013-07, Vol.771 (2), p.1-7
Main Authors: DE MOOIJ, E J W, Brogi, M, De Kok, R J, Snellen, I A G, Croll, B, Jayawardhana, R, Hoekstra, H, OTTEN, G P P L, Bekkers, D H, Haffert, S Y, Van Houdt, J J
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ATMOSPHERES
Band spectra
DENSITY
INT
LAYERS
Mathematical models
PLANETS
RAYLEIGH SCATTERING
SCALE HEIGHT
SPECTRA
STARS
TELESCOPES
Transit
TRANSMISSION
WATER
WAVELENGTHS
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Summary: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 + or - 0.0017, and in the g band 0.1180 + or - 0.0009 and 0.1174 + or - 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.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/771/2/109