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2025

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Title:	The KELT-7b atmospheric thermal-inversion conundrum revisited with CHEOPS, TESS, and additional data
Authors:	Z. Garai, A. Krenn, P. E. Cubillos, G. Bruno, A. M. S. Smith, T. G. Wilson, A. Brandeker, M. N. Gunther, A. Heitzmann, L. Carone, V. Singh, M. Lendl, O. D. S. Demangeon, Y. Alibert, R. Alonso, J. Asquier, T. Barczy, D. Barrado, S. C. C. Barros, W. Baumjohann, W. Benz, N. Billot, L. Borsato, C. Broeg, A. Collier Cameron, A. C. M. Correia, Sz. Csizmadia, M. B. Davies, M. Deleuil, A. Deline, B.-O. Demory, A. Derekas, B. Edwards, J. A. Egger, D. Ehrenreich, A. Erikson, J. Farinato, A. Fortier, L. Fossati, M. Fridlund, D. Gandolfi, K. Gazeas, M. Gillon, M. Gudel, Ch. Helling, K. G. Isaak, F. Kerschbaum, L. L. Kiss, J. Korth, K. W. F. Lam, J. Laskar, A. Lecavelier des Etangs, D. Magrin, P. F. L. Maxted, B. Merin, C. Mordasini, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Palle, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, G. Scandariato, D. Segransan, A. E. Simon, S. G. Sousa, M. Stalport, S. Sulis, Gy. M. Szabo, S. Udry, S. Ulmer-Moll, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton, S. Wolf, D. Wolter, T. Zingales
Image & caption:	Please click on image thumbnail to get more info: Image caption:: KELT-7b atmospheric retrieval of the infrared occultations. Top left panel: retrievals assuming thermochemical equilibrium with Pyrat Bay (blue) and PLATON (pink). Top right panel: retrieved T-P profiles for each software. The gray hatched area denotes the range of pressures probed by the observations. Bottom panels: same as above, but for the free-chemistry retrievals.
Description:	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 theoretical 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.
Reference:	Astronomy & Astrophysics, Vol. 700, A5, 26 pp.