The GTC exoplanet transit spectroscopy survey. VI. A spectrally-resolved Rayleigh scattering slope in GJ 3470b
| Autor: | Chen, G., Guenther, E. W., Palle, E., Nortmann, L., Nowak, G., Kunz, S., Parviainen, H., Murgas, F. |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | A&A 600, A138 (2017) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/201630228 |
| Popis: | Aims. As a sub-Uranus-mass low-density planet, GJ 3470b has been found to show a flat featureless transmission spectrum in the infrared and a tentative Rayleigh scattering slope in the optical. We conducted an optical transmission spectroscopy project to assess the impacts of stellar activity and to determine whether or not GJ 3470b hosts a hydrogen-rich gas envelop. Methods. We observed three transits with the low-resolution OSIRIS spectrograph at the 10.4 m Gran Telescopio Canarias, and one transit with the high-resolution UVES spectrograph at the 8.2 m Very Large Telescope. Results. From the high-resolution data, we find that the difference of the Ca II H+K lines in- and out-of-transit is only 0.67 +/- 0.22%, and determine a magnetic filling factor of about 10-15%. From the low-resolution data, we present the first optical transmission spectrum in the 435-755 nm band, which shows a slope consistent with Rayleigh scattering. Conclusions. After exploring the potential impacts of stellar activity in our observations, we confirm that Rayleigh scattering in an extended hydrogen/helium atmosphere is currently the best explanation. Further high-precision observations that simultaneously cover optical and infrared bands are required to answer whether or not clouds and hazes exist at high-altitude. Comment: 12 pages, 11 figures, accepted for publication in A&A |
| Databáze: | arXiv |
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