The stable climate of KELT-9b

• Published in: arXiv.org 2022-08
• Main Authors: Jones, K D, Morris, B M, B -O Demory, 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, Sz, Parviainen, H, Bruno, G, Alibert, Y, Alonso, R, Anglada, G, Bárczy, T, D Barrado y Navascues, Barros, S C C, Baumjohann, W, Beck, M, Beck, T, Benz, W, Bonfils, X, Brandeker, A, Broeg, C, Cabrera, J, Charnoz, S, A Collier Cameron, Davies, M B, Deleuil, M, Deline, A, Delrez, L, Erikson, A, tier, A, Fossati, L, Fridlund, M, Gandolfi, D, Gillon, M, Güdel, M, Isaak, K G, Kiss, L L, Laskar, J, A Lecavelier des Etangs, 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, Gy M, Thomas, N, Udry, S, V Van Grootel, Walter, I, Walton, N A, W Wang Jungo
• Format: Article
• Language: English
• Subjects: Albedo; Brightness temperature; Emission analysis; Energy transfer; Extrasolar planets; Gas giant planets; Irradiation; Space telescopes; Spaceborne telescopes; Thermal emission; Transits; Variability
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2208.04818

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 4500K. 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 30cm 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 \(\sim\)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% (1\(\sigma\)).