PREDNASAJUCI / LECTURER :

Zoltán Garai

(1) Astronomical Institute, Slovak Academy of Sciences,
059 60 Tatranská Lomnica

NAZOV / TITLE :

Is it thermally inverted or not? The KELT-7b atmospheric conundrum revisited
with CHEOPS, TESS, and additional data

ABSTRAKT / ABSTRACT :

Early theoretical works suggested that ultrahot Jupiters have inverted
temperature-pressure (T-P) profiles in the presence of optical absorbers,
such as TiO and VO. Recently, an inverted T-P profile of KELT-7b was detected,
in agreement with the predictions. However, the diagnosis of T-P inversions
has long been recognized as a model-dependent process. We used
the Characterising Exoplanet Satellite (CHEOPS), the Transiting Exoplanet
Survey Satellite (TESS), and additional literature data to characterize
the atmosphere of KELT-7b. We find that when adopting
a thermochemical-equilibrium atmospheric composition, the emission retrievals
return a non-inverted T-P profile, in contrast with previous results.
When adopting a free-chemistry atmospheric parameterization, the emission
retrievals return an inverted T-P profile. The 3D general circulation model
supports a TiO-induced temperature inversion. We can conclude that the choice
of a free-chemistry approach or a thermochemical-equilibrium chemistry is
the main factor determining the retrieval results. Free-chemistry retrievals
generally yield better fits; however, assuming free chemistry risks adopting
unphysical scenarios for ultrahot Jupiters, such as KELT-7b.