Transmission Spectroscopy of hot Jupiter WASP-19b

Regaining the FORS: optical ground-based transmission spectroscopy of the exoplanet WASP-19b with VLT+FORS2

Authors:

Sedaghati et al

Abstract:

Since a few years, the study of exoplanets has evolved from being purely discovery and exploratory in nature to being quite quantitative. In particular, transmission spectroscopy now allows the study of exoplanetary atmospheres. Such studies rely heavily on space-based or large ground-based facilities, as one needs to perform time-resolved, high signal-to-noise spectroscopy. The very recent exchange of the prisms of the FORS2 atmospheric diffraction corrector on ESO's Very Large Telescope should allow us to reach higher data quality than was possible before. With FORS2, we have obtained the first optical ground-based transmission spectrum of WASP-19b, with a 20 nm resolution in the 550--830 nm range. For this planet, the data set represents the highest resolution transmission spectrum obtained to date. We detect large deviations from planetary atmospheric models in the transmission spectrum redward of 790 nm, indicating the presence of additional sources of opacity not included in the current atmospheric models for WASP-19b, or additional, unexplored sources of systematics. Nonetheless, this work shows the new potential of FORS2 to study the atmospheres of exoplanets in greater detail than has been possible so far.