J/A+A/596/A47ivo://CDS.VizieR/J/A+A/596/A47doi:10.26093/cds/vizier.35960047CDSSedaghati E.Boffin H.M.J.Jerabkova T.Garcia Munoz A.Grenfell J.L.,Smette A.Ivanov V.D.Csizmadia Sz.Cabrera J.Kabath P.Rocchetto M.,Rauer H.2017-07-03T14:25:57Z2016-11-28T09:10:11ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmultiple-starssolar-system-planetsoccultationspectroscopyWe 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{AA} bins provides us with 'white' and spectrophotometric light curves, from 5700 to 8000{AA}. 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.2016A&A...596A..47Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/596/A47CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/709/159 : Relative Ic photometry of WASP-17 (Anderson+, 2010)J/MNRAS/426/1338 : Transiting planetary system WASP-17 (Southworth+, 2012)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/596/A47https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/596/A47http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/596/A47https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/596/A47https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/596/A47http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/596/A47GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/596/A47/lcdata*Normalised light curve fluxesF6400Normalized flux at bin centre 6400{AA}phot.flux;arith.ratiodoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime stamps of each observation, JD-2457192.5dtime.epochdoubleF5750Normalized flux at bin centre 5750{AA}phot.flux;arith.ratiodoubleF5800Normalized flux at bin centre 5800{AA}phot.flux;arith.ratiodoubleF5850Normalized flux at bin centre 5850{AA}phot.flux;arith.ratiodoubleF5900Normalized flux at bin centre 5900{AA}phot.flux;arith.ratiodoubleF5950Normalized flux at bin centre 5950{AA}phot.flux;arith.ratiodoubleF6000Normalized flux at bin centre 6000{AA}phot.flux;arith.ratiodoubleF6050Normalized flux at bin centre 6050{AA}phot.flux;arith.ratiodoubleF6100Normalized flux at bin centre 6100{AA}phot.flux;arith.ratiodoubleF6150Normalized flux at bin centre 6150{AA}phot.flux;arith.ratiodoubleF6200Normalized flux at bin centre 6200{AA}phot.flux;arith.ratiodoubleF6250Normalized flux at bin centre 6250{AA}phot.flux;arith.ratiodoubleF6300Normalized flux at bin centre 6300{AA}phot.flux;arith.ratiodoubleF6350Normalized flux at bin centre 6350{AA}phot.flux;arith.ratiodoubleF6450Normalized flux at bin centre 6450{AA}phot.flux;arith.ratiodoubleF6500Normalized flux at bin centre 6500{AA}phot.flux;arith.ratiodoubleF6550Normalized flux at bin centre 6550{AA}phot.flux;arith.ratiodoubleF6600Normalized flux at bin centre 6600{AA}phot.flux;arith.ratiodoubleF6650Normalized flux at bin centre 6650{AA}phot.flux;arith.ratiodoubleF6700Normalized flux at bin centre 6700{AA}phot.flux;arith.ratiodoubleF6750Normalized flux at bin centre 6750{AA}phot.flux;arith.ratiodoubleF6800Normalized flux at bin centre 6800{AA}phot.flux;arith.ratiodoubleF6850Normalized flux at bin centre 6850{AA}phot.flux;arith.ratiodoubleF6900Normalized flux at bin centre 6900{AA}phot.flux;arith.ratiodoubleF6950Normalized flux at bin centre 6950{AA}phot.flux;arith.ratiodoubleF7000Normalized flux at bin centre 7000{AA}phot.flux;arith.ratiodoubleF7050Normalized flux at bin centre 7050{AA}phot.flux;arith.ratiodoubleF7100Normalized flux at bin centre 7100{AA}phot.flux;arith.ratiodoubleF7150Normalized flux at bin centre 7150{AA}phot.flux;arith.ratiodoubleF7200Normalized flux at bin centre 7200{AA}phot.flux;arith.ratiodoubleF7250Normalized flux at bin centre 7250{AA}phot.flux;arith.ratiodoubleF7300Normalized flux at bin centre 7300{AA}phot.flux;arith.ratiodoubleF7350Normalized flux at bin centre 7350{AA}phot.flux;arith.ratiodoubleF7400Normalized flux at bin centre 7400{AA}phot.flux;arith.ratiodoubleF7450Normalized flux at bin centre 7450{AA}phot.flux;arith.ratiodoubleF7500Normalized flux at bin centre 7500{AA}phot.flux;arith.ratiodoubleF7550Normalized flux at bin centre 7550{AA}phot.flux;arith.ratiodoubleF7600Normalized flux at bin centre 7600{AA}phot.flux;arith.ratiodoubleF7650Normalized flux at bin centre 7650{AA}phot.flux;arith.ratiodoubleF7700Normalized flux at bin centre 7700{AA}phot.flux;arith.ratiodoubleF7750Normalized flux at bin centre 7750{AA}phot.flux;arith.ratiodoubleF7800Normalized flux at bin centre 7800{AA}phot.flux;arith.ratiodoubleF7850Normalized flux at bin centre 7850{AA}phot.flux;arith.ratiodoubleF7900Normalized flux at bin centre 7900{AA}phot.flux;arith.ratiodoubleF7950Normalized flux at bin centre 7950{AA}phot.flux;arith.ratiodouble