Alkali metals in exoplanet atmospheres

Exoplanet atmospheres could carry chemical imprints (e.g. metallicity, C/O ratio) to link to planet formation and evolution history. While a large collection of exoplanets have exhibited the water absorption signature at 1.4 micron as probed by HST/WFC3, the determination of water abundances is somewhat hindered by the potential presence of clouds and hazes owing to the degeneracy between pressure and abundance. Fortunately, clear atmospheres could exhibit two major characteristics: Rayleigh scattering from molecular hydrogen and pressure-broadened absorption line wings of alkali metals, which are easily probed by optical transmission spectroscopy. In this talk, I will present the latest results from our transit spectroscopy survey using the low-resolution optical spectrograph at the 10.4 meter GTC telescope. One of the highlights is that we recently detected Na, K, and Li in a super-Neptune and spectrally resolved the pressure-broadened wings of Na and K. This is not only the first time that multiple alkali metals are robustly detected in an exoplanet, but also the first time that lithium is detected in an exoplanet. In addition, I will also present our efforts in using high-dispersion spectrographs (e.g. HARPS-N, CARMENES) to characterize the absorption line cores of alkali metals.  

Speaker: 
CHEN Guo (PMO)
Location: 
first floor meeting room, KIAA
Time: 
Wed, 2018-07-18 12:00 to 13:00