We investigated the potassium excess absorption around 7699 Å of the exoplanets HD189733b and HD209458b using high-spectral resolution transit observations acquired with the 2 × 8.4 m Large Binocular Telescope (LBT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI). For a bandwidth of 0.8 Å, we present a detection >7σ with an absorption level of 0.18 per cent for HD189733b. Applying the same analysis to HD209458b, we can set 3σ upper limit of 0.09 per cent, even though a K-excess absorption was not detected. The investigation suggests that the K feature is less present in the atmosphere of HD209458b than in the one of HD189733b and confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.
Read more: Keles et al. 2019, MNRAS, 489, L37