2023MNRAS.522.1491S

Hot Jupiters, particularly those with temperature higher than 2000 K, are the best sample of planets that allow in-depth characterization of their atmospheres. We present here a thermal emission study of the ultrahot Jupiter WASP-103 b observed in two secondary eclipses with CFHT/WIRCam in J and K_s bands. By means of high precision differential photometry, we determine eclipse depths in J and K_s to an accuracy of 220 and 270 ppm, which are combined with the published HST/WFC3 and Spitzer data to retrieve a joint constraints on the properties of WASP-103 b dayside atmosphere. We find that the atmosphere is best fit with a thermal inversion layer included. The equilibrium chemistry retrieval indicates an enhanced C/O (1.35$^{+0.14}_{-0.17}$) and a supermetallicity with [Fe/H]$=2.19^{+0.51}_{-0.63}$ composition. Given the near-solar metallicity of WASP-103 of [Fe/H] = 0.06, this planet seems to be ∼100 more abundant than its host star. The free chemistry retrieval analysis yields a large abundance of FeH, H^–, CO₂, and CH₄. Additional data of better accuracy from future observations of JWST should provide better constraint of the atmospheric properties of WASP-103b.