Potassium detection in the clear atmosphere of a hot-Jupiter FORS2 transmission spectroscopy of WASP-17b

被引:40
作者
Sedaghati, E. [1 ,2 ,3 ]
Boffin, H. M. J. [1 ,4 ]
Jerabkova, T. [5 ,6 ]
Munoz, A. Garcia [3 ]
Grenfell, J. L. [2 ,3 ]
Smette, A. [1 ]
Ivanov, V. D. [1 ,4 ]
Csizmadia, Sz. [2 ]
Cabrera, J. [2 ]
Kabath, P. [6 ]
Rocchetto, M. [7 ]
Rauer, H. [2 ,3 ]
机构
[1] European Southern Observ, Alonso Cordova 3107, Santiago 19001, Chile
[2] Deutsch Zentrum Luft & Raumfahrt, Inst Planetenforsch, Rutherfordstr 2, D-12489 Berlin, Germany
[3] Tech Univ Berlin, Zentrum Astron & Astrophys, Hardenbergstr 36, D-10623 Berlin, Germany
[4] European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany
[5] Charles Univ Prague, Astron Inst, Vholesovickach 2, Prague 18000 8, Czech Republic
[6] Astron Inst ASCR, Fricova 298, Ondrejov 25165, Czech Republic
[7] UCL, Dept Phys & Astron, Gower St, London WC1E 6BT, England
来源
ASTRONOMY & ASTROPHYSICS | 2016年 / 596卷
基金
欧洲研究理事会;
关键词
planets and satellites: atmospheres; planets and satellites: individual: WASP-17b; techniques: spectroscopic; instrumentation: spectrographs; stars: individual: WASP-17; methods: data analysis; HUBBLE-SPACE-TELESCOPE; HD; 189733B; MULTIOBJECT SPECTROGRAPH; LIGHT CURVES; GJ; 1214B; SPECTRUM; PLANET; SODIUM; EARTH; PHOTOMETRY;
D O I
10.1051/0004-6361/201629090
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present FORS2 (attached to ESO's Very Large Telescope) observations of the exoplanet WASP-17b during its primary transit, for the purpose of differential spectrophotometry analysis. We use the instrument in its Mask eXchange Unit (MXU) mode to simultaneously obtain low resolution spectra of the planet hosting star, as well as several reference stars in the field of view. The integration of these spectra within broadband and smaller 100 angstrom bins provides us with "white" and spectrophotometric light curves, from 5700 to 8000 angstrom. Through modelling the white light curve, we obtain refined bulk and transit parameters of the planet, as well as wavelength-dependent variations of the planetary radius from smaller spectral bins through which the transmission spectrum is obtained. The inference of transit parameters, as well as the noise statistics, is performed using a Gaussian Process model. We achieve a typical precision in the transit depth of a few hundred parts per million from various transit light curves. From the transmission spectra we rule out a flat spectrum at >3 sigma and detect marginal presence of the pressure-broadened sodium wings. Furthermore, we detect the wing of the potassium absorption line in the upper atmosphere of the planet with 3 sigma confidence, both facts pointing to a relatively shallow temperature gradient in the atmosphere. These conclusions are mostly consistent with previous studies of this exo-atmosphere, although previous potassium measurements have been inconclusive.
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页数:14
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