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VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground

Nikolov, N; Sing, D; Gibson, N; Fortney, J; Evans, TM; Eberhardt, JK; Kataria, T; (2016) VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground. The Astrophysical Journal , 832 (2) , Article 191. 10.3847/0004-637X/832/2/191. Green open access

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Abstract

We present transmission spectroscopy of the warm Saturn-mass exoplanet WASP-39b made with the Very Large Telescope FOcal Reducer and Spectrograph (FORS2) across the wavelength range 411–810 nm. The transit depth is measured with a typical precision of 240 parts per million (ppm) in wavelength bins of 10 nm on a V = 12.1 mag star. We detect the sodium absorption feature (3.2σ) and find evidence of potassium. The ground-based transmission spectrum is consistent with Hubble Space Telescope (HST) optical spectroscopy, supporting the interpretation that WASP-39b has a largely clear atmosphere. Our results demonstrate the great potential of the recently upgraded FORS2 spectrograph for optical transmission spectroscopy, with which we obtained HST-quality light curves from the ground.

Type: Article
Title: VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/0004-637X/832/2/191
Publisher version: http://doi.org/10.3847/0004-637X/832/2/191
Language: English
Additional information: © 2016. The American Astronomical Society. All rights reserved.
Keywords: Planets and satellites: atmospheres; stars: individual (WASP-39); techniques: photometric; techniques: spectroscopic
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1529980
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