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

N. Nikolov, David K. Sing, Neale P. Gibson, J. J. Fortney, Thomas M. Evans, Joanne K. Barstow, Tiffany Kataria, Paul A. Wilson

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Abstract

We present transmission spectroscopy of the warm Saturn-mass exoplanet WASP-39b made with the Very Large Telescope (VLT) FOcal Reducer and Spectrograph (FORS2) across the wavelength range 411-810nm. The transit depth is measured with a typical precision of 240 parts per million (ppm) in wavelength bins of 10nm on a V = 12.1 magnitude star. We detect the sodium absorption feature (3.2-sigma) and find evidence for potassium. The ground-based transmission spectrum is consistent with Hubble Space Telescope (HST) optical spectroscopy, strengthening the interpretation of WASP-39b having a largely clear atmosphere. Our results demonstrate the great potential of the recently upgraded FORS2 spectrograph for optical transmission spectroscopy, obtaining HST-quality light curves from the ground.
Original languageEnglish
JournalThe Astrophysical Journal
Volume832
Issue number2
DOIs
Publication statusPublished - 01 Dec 2016

Keywords

  • Astrophysics - Earth and Planetary Astrophysics

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