Thermal emission spectra of the ultra-hot Jupiter WASP-33 b

Observations of exoplanetary atmospheres provide critical insights into their chemical composition, formation, and evolution history. Ultra-hot Jupiters serve as excellent targets for atmospheric characterization; studies of these planets may yield key understanding of gas giants’ formation and evolution history. We present a thermal emission study of WASP-33 b’s dayside atmosphere, based on two secondary eclipse observations with CFHT/WIRCam in two specific narrow band filters, namely the CO and CH4 on filters, and archival data with HST/WFC3 and Spitzer. Stellar pulsations of the host star induce some quasi-periodic photometric variations, particularly in the CH4 on band, which are modeled and corrected in the high-precision differential light curves. An eclipse depth of 1565.2 −237.5 +228.6 ppm and 914.3 −57.0 +56.1 ppm is determined for the CO and CH4 on bands, respectively. Combined with HST/WFC3 and Spitzer data, our joint retrieval of WASP-33 b’s dayside atmosphere reveals a high metallicity ([Fe/H] = 1.52 −0.52 +0.35 ), high C/O ratio (C/O = 0.78 −0.04 +0.03 ), and a thermal inversion layer, suggesting a formation history involving metal-rich gas accretion. We confirm the presence of the molecules H 2 O, H + and CO, and report a tentative detection of TiO in the dayside atmosphere of WASP-33 b. Future higher precision observations with JWST may provide better understanding of constraints on the chemical abundances of oxygen and refractory element abundances to better constrain WASP-33 b’s formation and evolutionary pathway.