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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%

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

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https://hal-insu.archives-ouvertes.fr/insu-03839239
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Friday, November 4, 2022 - 11:43:16 AM
Last modification on : Tuesday, December 6, 2022 - 12:42:14 PM

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Distributed under a Creative Commons Attribution 4.0 International License

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K. Jones, B. M. Morris, B. -O. Demory, K. Heng, M. J. Hooton, et al.. The stable climate of KELT-9b,★. Astronomy and Astrophysics - A&A, 2022, 666, ⟨10.1051/0004-6361/202243823⟩. ⟨insu-03839239⟩

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