@article{KelesMallomvonEssenetal.2021,
  author    = {Keles, Engin and Mallom, Matthias and von Essen, Carolina and Caroll, Thorsten A. and Alexoudi, Xanthippi and Pino, Lorenzo and Ilyin, Ilya and Poppenh{\"a}ger, Katja and Kitzmann, Daniel and Nascimbeni, Valerino and Turner, Jake D. and Strassmeier, Klaus G.},
  title     = {The potassium absorption on HD189733b and HD209458b},
  series = {Monthly Notices of the Royal Astronomical Society: Letters},
  volume    = {489},
  journal   = {Monthly Notices of the Royal Astronomical Society: Letters},
  number    = {1},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  doi       = {10.1093/mnrasl/slz123},
  pages     = {L37 -- L41},
  year      = {2021},
  abstract  = {In this work, we investigate the potassium excess absorption around 7699 {\AA} of the exoplanets HD189733b and HD209458b. For this purpose, we used 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 {\AA}, 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 we do not detect a K-excess absorption. The investigation suggests that the K feature is less present in the atmosphere of HD209458b than in the one of HD189733b. This comparison confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.},
  language  = {en}
}
@article{KelesKitzmannMallonnetal.2020,
  author    = {Keles, Engin and Kitzmann, Daniel and Mallonn, Matthias and Alexoudi, Xanthippi and Fossati, Luca and Pino, Lorenzo and Seidel, Julia Victoria and Caroll, Thorsten A. and Steffen, M. and Ilyin, Ilya and Poppenh{\"a}ger, Katja and Strassmeier, Klaus G. and von Essen, Carolina and Nascimbeni, Valerio and Turner, Jake D.},
  title     = {Probing the atmosphere of HD189733b with the Na i and K i lines},
  series = {Monthly Notices of the Royal Astronomical Society},
  volume    = {498},
  journal   = {Monthly Notices of the Royal Astronomical Society},
  number    = {1},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  doi       = {10.1093/mnras/staa2435},
  pages     = {1033},
  year      = {2020},
  abstract  = {High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high-altitude absorption, e.g. from resonant sodium (Na i) and potassium (K i) lines. We resolve the atmospheric K i absorption on HD189733b with the aim to compare the resolved K i line and previously obtained high-resolution Na i-D line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of ∼10 km/s for the Na i-D lines and only a few km/s for the K i line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K i or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.},
  language  = {en}
}