2 research outputs found
VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground
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.Comment: 11 pages, 5 figures, accepted for publication in Ap