The stable climate of KELT-9b
Alonso, R.; Deleuil, M.; Erikson, A.; Fridlund, M.; Queloz, D.; Rauer, H.; Olofsson, G.; Pallé, E.; Ribas, I.; Heng, K.; Güdel, M.; Isaak, K. G.; Scandariato, G.; Pagano, I.; Steller, M.; Thomas, N.; Baumjohann, W.; Gandolfi, D.; Fossati, L.; Csizmadia, Sz.; Smith, A. M. S.; Cabrera, J.; Ségransan, D.; Walton, N. A.; Ragazzoni, R.; Piotto, G.; Benz, W.; Deline, A.; Collier Cameron, A.; Alibert, Y.; Delrez, L.; Fortier, A.; Hoyer, S.; Bonfanti, A.; Salmon, S.; Sousa, S. G.; Wilson, T. G.; Bárczy, T.; Barrado, D.; Barros, S. C. C.; Beck, M.; Beck, T.; Billot, N.; Bonfils, X.; Brandeker, A.; Broeg, C.; Charnoz, S.; Davies, M. B.; Demangeon, O. D. S.; Demory, B. -O.; Ehrenreich, D.; Gillon, M.; Hooton, M. J.; Kiss, L. L.; Laskar, J.; Lecavelier des Etangs, A.; Lendl, M.; Lovis, C.; Magrin, D.; Maxted, P. F. L.; Nascimbeni, V.; Ottensamer, R.; Peter, G.; Pollacco, D.; Rando, N.; Santos, N. C.; Simon, A. E.; Szabó, Gy. M.; Udry, S.; Van Grootel, V.; Anglada, G.; Ratti, F.; Parviainen, H.; Morris, B. M.; Bruno, G.; Walter, I.; Jones, K.; Reimers, C.; Wang Jungo, W.
Switzerland, United Kingdom, France, Portugal, Austria, Germany, Spain, Italy, Hungary, Sweden, Belgium, Netherlands
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%
The photometric time series data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/666/A118