Contributed Talk - Splinter Exoplanets

Thursday, 24 September 2020, 16:35   (virtual room D)

High-resolution Transmission Spectroscopy of Four Hot Inflated Gas Giant Exoplanets

Jiri Zak (1, 2), Petr Kabath (2), Henri M.J. Boffin (1), Valentin D. Ivanov (1) and Marek Skarka (2)
(1) ESO, (2) Astronomical Institute, Czech Academy of Sciences, Ondrejov, Czech Republic

The technique of transmission spectroscopy allows us to constrain the chemical composition and to study the physicochemical processes in the atmospheres of transiting exoplanets. High-resolution transmission spectroscopy relies on very high signal-to-noise observations and is thus most suited for bright exoplanet host stars. In the era of the Transiting Exoplanet Survey Satellite (TESS), and PLAnetary Transits and Oscillations of stars (PLATO), more and more suitable targets, even for mid-sized telescopes, are discovered. Furthermore, a wealth of archival data is available that could become a basis for long-term monitoring of exoatmospheres to study their variability. We analyzed archival HARPS spectroscopic time series of four host stars to transiting bloated gas exoplanets, namely WASP-76b, WASP-127b, WASP-166b, and KELT-11b, searching for traces of sodium, neutral hydrogen, and lithium. By comparing the in- and out-of-transit spectra we can filter out the stellar lines and investigate the absorption from the planet. Simultaneously, the stellar activity is monitored using the Mg I and Ca I lines. We detect sodium in the atmosphere of WASP-76b at a 7-9sigma level. Furthermore, we report also at a 4-8sigma level of significance the detection of sodium in the atmosphere of WASP-127b, confirming earlier results based on low-resolution spectroscopy. Our analysis shows no sodium nor any other atom at high confidence levels for WASP-166b nor KELT-11b, hinting at the presence of high clouds. We will also discuss the apparent reason for the discrepancy between our result on WASP-166b and recent work that detected Na in the planetary atmosphere. Finally, we will present some preliminary results on a few selected targets.