Presentation #102.128 in the session Poster Session.
Even among the most irradiated gas giants, so-called ultra hot Jupiters (UHJs), KELT-9b stands out as the hottest planet thus far discovered with a dayside temperature of over 4500K. UHJs are a newly-emerging class of short-period exoplanets and chemically, are objects in between gas-giant exoplanets and stars. At these extreme irradiation levels, molecular hydrogen dissociation occurring on the planetary dayside is expected to influence the heat redistribution and reflective properties of the atmosphere.
We present 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 the 4 CHEOPS phase curves as well as optical phase curves from TESS and an infrared phase curve from Spitzer to infer joint constraints on the phase curve variation, gravity-darkened transits, and occultation depth in three bandpasses. We derive 2D temperature maps of the atmosphere at three different atmospheric layers and use these to investigate the thermal and dynamic characteristics of the planet.
Our results provide insights into the climate and atmospheric variability of KELT-9b and continue the work of investigating the properties of ultra-hot Jupiters. They are also particularly relevant for future work focussed on analysing and combining multi-wavelength phase curves from the recently launched James Webb Space Telescope.