Probing the emission spectra of two ultra-hot Jupiters using ground-based occultation photometry (contributed talk)

By observing the occultation (secondary eclipse) of a transiting exoplanet by its host star inthe (near-)infrared, the thermal emission of its dayside can be retrieved. Using this techniqueat different wavelengths in the (near-)infrared allows to probe the emission spectrum ofthe planet’s dayside, from which insights on the vertical thermal structure and chemicalcomposition of its atmosphere can be gained. Very hot and inflated gas giants in very-short-period orbits around their stars are the most favorable targets for such measurements,thanks to their high temperature and large size. The atmospheres of such ultra-hot Jupitersare expected to be conducive for gaseous TiO and VO, which could cause thermal inversions(i.e. stratospheres) by reprocessing incident UV/visible irradiation to heat in the upperatmospheric layers. Thermal inversions have been previously claimed for several hot Jupitersbased on Spitzer observations, but these results were recently found to suffer from significantsystematic biases and were thus seriously called into question. Nevertheless, hottest planetsare still the best candidates to host thermal inversions in their dayside atmospheres, theonly planet showing clear evidence for a temperature inversion to date being WASP-33b,which is one of the most highly irradiated hot Jupiters currently known. In this talk, Iwill present results of an intense ground-based photometric campaign aiming at probing theemission spectra of WASP-103b and WASP-121b, two ultra-hot Jupiters orbiting their hoststars just beyond the Roche limit.