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The KELT-7b atmospheric thermal-inversion conundrum revisited with CHEOPS, TESS, and additional data

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Main Authors:	Garai, Z., Krenn, A., Cubillos, P. E., Bruno, G., Smith, A. M. S., Wilson, T. G., Brandeker, A., Günther, M. N., Heitzmann, A., Carone, L., Singh, V., Lendl, M., Demangeon, O. D. S., Alibert, Y., Alonso, R., Asquier, J., Bárczy, T., Barrado, D., Barros, S. C., Baumjohann, W., Benz, W., Billot, N., Borsato, L., Broeg, C., Cameron, A. Collier, Correia, A. C. M., Csizmadia, Sz., Davies, M. B., Deleuil, M., Deline, A., Demory, B. -O., Derekas, A., Edwards, B., Egger, J. A., Ehrenreich, D., Erikson, A., Farinato, J., Fortier, A., Fossati, L., Fridlund, M., Gandolfi, D., Gazeas, K., Gillon, M., Güdel, M., Helling, Ch., Isaak, K. G., Kerschbaum, F., Kiss, L., Korth, J., Lam, K. W. F., Laskar, J., Etangs, A. Lecavelier des, Magrin, D., Maxted, P. F. L., Merín, B., Mordasini, C., Nascimbeni, V., Olofsson, G., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piazza, D., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Santos, N. C., Scandariato, G., Ségransan, D., Simon, A. E., Sousa, S. G., Stalport, M., Sulis, S., Szabó, M. Gy., Udry, S., Ulmer-Moll, S., Van Grootel, V., Venturini, J., Villaver, E., Walton, N. A., Wolf, S., Wolter, D., Zingales, T.
Format:	Preprint
Published:	2025
Subjects:	Earth and Planetary Astrophysics
Online Access:	Acceder al recurso
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_version_	1866916810849255424
author	Garai, Z. Krenn, A. Cubillos, P. E. Bruno, G. Smith, A. M. S. Wilson, T. G. Brandeker, A. Günther, M. N. Heitzmann, A. Carone, L. Singh, V. Lendl, M. Demangeon, O. D. S. Alibert, Y. Alonso, R. Asquier, J. Bárczy, T. Barrado, D. Barros, S. C. Baumjohann, W. Benz, W. Billot, N. Borsato, L. Broeg, C. Cameron, A. Collier Correia, A. C. M. Csizmadia, Sz. Davies, M. B. Deleuil, M. Deline, A. Demory, B. -O. Derekas, A. Edwards, B. Egger, J. A. Ehrenreich, D. Erikson, A. Farinato, J. Fortier, A. Fossati, L. Fridlund, M. Gandolfi, D. Gazeas, K. Gillon, M. Güdel, M. Helling, Ch. Isaak, K. G. Kerschbaum, F. Kiss, L. Korth, J. Lam, K. W. F. Laskar, J. Etangs, A. Lecavelier des Magrin, D. Maxted, P. F. L. Merín, B. Mordasini, C. Nascimbeni, V. Olofsson, G. Ottensamer, R. Pagano, I. Pallé, E. Peter, G. Piazza, D. Piotto, G. Pollacco, D. Queloz, D. Ragazzoni, R. Rando, N. Rauer, H. Ribas, I. Santos, N. C. Scandariato, G. Ségransan, D. Simon, A. E. Sousa, S. G. Stalport, M. Sulis, S. Szabó, M. Gy. Udry, S. Ulmer-Moll, S. Van Grootel, V. Venturini, J. Villaver, E. Walton, N. A. Wolf, S. Wolter, D. Zingales, T.
author_facet	Garai, Z. Krenn, A. Cubillos, P. E. Bruno, G. Smith, A. M. S. Wilson, T. G. Brandeker, A. Günther, M. N. Heitzmann, A. Carone, L. Singh, V. Lendl, M. Demangeon, O. D. S. Alibert, Y. Alonso, R. Asquier, J. Bárczy, T. Barrado, D. Barros, S. C. Baumjohann, W. Benz, W. Billot, N. Borsato, L. Broeg, C. Cameron, A. Collier Correia, A. C. M. Csizmadia, Sz. Davies, M. B. Deleuil, M. Deline, A. Demory, B. -O. Derekas, A. Edwards, B. Egger, J. A. Ehrenreich, D. Erikson, A. Farinato, J. Fortier, A. Fossati, L. Fridlund, M. Gandolfi, D. Gazeas, K. Gillon, M. Güdel, M. Helling, Ch. Isaak, K. G. Kerschbaum, F. Kiss, L. Korth, J. Lam, K. W. F. Laskar, J. Etangs, A. Lecavelier des Magrin, D. Maxted, P. F. L. Merín, B. Mordasini, C. Nascimbeni, V. Olofsson, G. Ottensamer, R. Pagano, I. Pallé, E. Peter, G. Piazza, D. Piotto, G. Pollacco, D. Queloz, D. Ragazzoni, R. Rando, N. Rauer, H. Ribas, I. Santos, N. C. Scandariato, G. Ségransan, D. Simon, A. E. Sousa, S. G. Stalport, M. Sulis, S. Szabó, M. Gy. Udry, S. Ulmer-Moll, S. Van Grootel, V. Venturini, J. Villaver, E. Walton, N. A. Wolf, S. Wolter, D. Zingales, T.
contents	Ultrahot Jupiters are predicted to show inverted temperature-pressure (T-P) profiles in the presence of optical absorbers such as TiO and VO. An inverted T-P profile of KELT-7b was recently detected, in line with these predictions, but such diagnoses are known to be model-dependent. We used CHEOPS, TESS, and literature data to characterize the atmosphere of KELT-7b, reassess its T-P profile, measure its albedo, and search for distortions in its CHEOPS transit light curve due to stellar rotation. We jointly fitted CHEOPS and TESS data to measure the occultation depths and modeled CHEOPS transits including gravity darkening. Emission and transmission retrievals were performed, and the albedo was calculated in the CHEOPS and TESS passbands. Thermochemical-equilibrium retrievals yield a non-inverted T-P profile, while free-chemistry retrievals yield an inverted profile with likely unphysical TiO/VO abundances. A 3D GCM supports a TiO-driven inversion. We report a low geometric albedo of $A_\mathrm{g} = 0.05 \pm 0.06$, consistent with inefficient heat redistribution and supported by a GCM with magnetic drag. CHEOPS data provide no constraint on the sky-projected orbital obliquity. Retrieval results strongly depend on the chemical framework. Free-chemistry fits are better but risk unphysical solutions for ultrahot Jupiters. We applied a coherent stellar variability correction to CHEOPS and TESS data; future observations would benefit from similar treatment.
format	Preprint
id	arxiv_https___arxiv_org_abs_2506_20432
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	The KELT-7b atmospheric thermal-inversion conundrum revisited with CHEOPS, TESS, and additional data Garai, Z. Krenn, A. Cubillos, P. E. Bruno, G. Smith, A. M. S. Wilson, T. G. Brandeker, A. Günther, M. N. Heitzmann, A. Carone, L. Singh, V. Lendl, M. Demangeon, O. D. S. Alibert, Y. Alonso, R. Asquier, J. Bárczy, T. Barrado, D. Barros, S. C. Baumjohann, W. Benz, W. Billot, N. Borsato, L. Broeg, C. Cameron, A. Collier Correia, A. C. M. Csizmadia, Sz. Davies, M. B. Deleuil, M. Deline, A. Demory, B. -O. Derekas, A. Edwards, B. Egger, J. A. Ehrenreich, D. Erikson, A. Farinato, J. Fortier, A. Fossati, L. Fridlund, M. Gandolfi, D. Gazeas, K. Gillon, M. Güdel, M. Helling, Ch. Isaak, K. G. Kerschbaum, F. Kiss, L. Korth, J. Lam, K. W. F. Laskar, J. Etangs, A. Lecavelier des Magrin, D. Maxted, P. F. L. Merín, B. Mordasini, C. Nascimbeni, V. Olofsson, G. Ottensamer, R. Pagano, I. Pallé, E. Peter, G. Piazza, D. Piotto, G. Pollacco, D. Queloz, D. Ragazzoni, R. Rando, N. Rauer, H. Ribas, I. Santos, N. C. Scandariato, G. Ségransan, D. Simon, A. E. Sousa, S. G. Stalport, M. Sulis, S. Szabó, M. Gy. Udry, S. Ulmer-Moll, S. Van Grootel, V. Venturini, J. Villaver, E. Walton, N. A. Wolf, S. Wolter, D. Zingales, T. Earth and Planetary Astrophysics Ultrahot Jupiters are predicted to show inverted temperature-pressure (T-P) profiles in the presence of optical absorbers such as TiO and VO. An inverted T-P profile of KELT-7b was recently detected, in line with these predictions, but such diagnoses are known to be model-dependent. We used CHEOPS, TESS, and literature data to characterize the atmosphere of KELT-7b, reassess its T-P profile, measure its albedo, and search for distortions in its CHEOPS transit light curve due to stellar rotation. We jointly fitted CHEOPS and TESS data to measure the occultation depths and modeled CHEOPS transits including gravity darkening. Emission and transmission retrievals were performed, and the albedo was calculated in the CHEOPS and TESS passbands. Thermochemical-equilibrium retrievals yield a non-inverted T-P profile, while free-chemistry retrievals yield an inverted profile with likely unphysical TiO/VO abundances. A 3D GCM supports a TiO-driven inversion. We report a low geometric albedo of $A_\mathrm{g} = 0.05 \pm 0.06$, consistent with inefficient heat redistribution and supported by a GCM with magnetic drag. CHEOPS data provide no constraint on the sky-projected orbital obliquity. Retrieval results strongly depend on the chemical framework. Free-chemistry fits are better but risk unphysical solutions for ultrahot Jupiters. We applied a coherent stellar variability correction to CHEOPS and TESS data; future observations would benefit from similar treatment.
title	The KELT-7b atmospheric thermal-inversion conundrum revisited with CHEOPS, TESS, and additional data
topic	Earth and Planetary Astrophysics
url	https://arxiv.org/abs/2506.20432