GTC transit light curves of WASP-127b

Alkali metals have been long suggested to exhibit broad wings due to pressure broadening, but most of the alkali detections only show very narrow absorption cores, probably due to the presence of clouds. Here we report the strong detection of the pressure-broadened spectral profiles of Na, K, and Li absorption in the atmosphere of the super-Neptune WASP-127b, at 5.0{sigma}, 4.1{sigma}, and 3.4{sigma}, respectively.

We performed a spectral retrieval modeling on the high-quality optical transmission spectrum newly acquired with the 10.4m Gran Telescopio Canarias (GTC), in combination with the re-analyzed optical transmission spectrum obtained with the 2.5m Nordic Optical Telescope (NOT). By assuming a patchy cloudy model, we retrieved the abundances of Na, K, and Li, which are super-solar at 3.7{sigma} for K and 5.1{sigma} for Li (and only 1.8{sigma} for Na).