The stable climate of KELT-9b
Abstract
Even among the most irradiated gas giants, so-called ultra-hot Jupiters, KELT-9b stands out as the hottest planet thus far discovered with a dayside temperature of over 4500 K. At these extreme irradiation levels, we expect an increase in heat redistribution efficiency and a low Bond albedo owed to an extended atmosphere with molecular hydrogen dissociation occurring on the planetary dayside. We present new photometric observations of the KELT-9 system throughout 4 full orbits and 9 separate occultations obtained by the 30 cm space telescope CHEOPS. The CHEOPS bandpass, located at optical wavelengths, captures the peak of the thermal emission spectrum of KELT-9b. In this work we simultaneously analyse CHEOPS phase curves along with public phase curves from TESS and Spitzer to infer joint constraints on the phase curve variation, gravity-darkened transits, and occultation depth in three bandpasses, as well as derive 2D temperature maps of the atmosphere at three different depths. We find a day-night heat redistribution efficiency of ~0.3 which confirms expectations of enhanced energy transfer to the planetary nightside due to dissociation and recombination of molecular hydrogen. We also calculate a Bond albedo consistent with zero. We find no evidence of variability of the brightness temperature of the planet, excluding variability greater than 1%.
Citation
Jones , K , Morris , B M , Demory , B-O , Heng , K , Hooton , M J , Billot , N , Ehrenreich , D , Hoyer , S , Simon , A E , Lendl , M , Demangeon , O D S , Sousa , S G , Bonfanti , A , Wilson , T G , Salmon , S , Csizmadia , S , Parviainen , H , Bruno , G , Alibert , Y , Alonso , R , Anglada , G , Bárczy , T , Barrado , D , Barros , S C C , Baumjohann , W , Beck , M , Beck , T , Benz , W , Bonfils , X , Brandeker , A , Broeg , C , Cabrera , J , Charnoz , S , Collier Cameron , A , Davies , M B , Deleuil , M , Deline , A , Delrez , L , Erikson , A , Fortier , A , Fossati , L , Fridlund , M , Gandolfi , D , Gillon , M , Güdel , M , Isaak , K G , Kiss , L L , Laskar , J , Lecavelier des Etangs , A , Lovis , C , Magrin , D , Maxted , P F L , Nascimbeni , V , Olofsson , G , Ottensamer , R , Pagano , I , Pallé , E , Peter , G , Piotto , G , Pollacco , D , Queloz , D , Ragazzoni , R , Rando , N , Ratti , F , Rauer , H , Reimers , C , Ribas , I , Santos , N C , Scandariato , G , Ségransan , D , Smith , A M S , Steller , M , Szabó , G M , Thomas , N , Udry , S , Van Grootel , V , Walter , I , Walton , N A & Wang Jungo , W 2022 , ' The stable climate of KELT-9b ' , Astronomy & Astrophysics , vol. 666 , A118 . https://doi.org/10.1051/0004-6361/202243823
Publication
Astronomy & Astrophysics
Status
Peer reviewed
ISSN
0004-6361Type
Journal article
Rights
Copyright © K. Jones et al. 2022. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Description
Funding: A.C.C. and T.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1.Collections
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