A Joint Retrieval on the High- and Low-resolution Transmission Spectra of the Hot Jupiter WASP-62b

The hot Jupiter WASP-62b is one of the few known exoplanets possessing clear-sky signatures, making it an ideal target for investigating the physical and chemical properties of hot gas giant atmospheres. This work aims to perform a joint retrieval analysis of the atmospheric parameters of WASP-62b by combining ground-based high-resolution and space-based low-resolution spectroscopic data, thereby obtaining more comprehensive constraints on its atmospheric properties. Based on high-resolution observations from the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph, the line cores of the Na doublet were successfully resolved. The detected radial velocity variation is consistent with the planetary orbital motion, confirming that the signal originates from the planetary atmosphere. Furthermore, the joint retrieval analysis of high- and low-resolution transmission spectra indicates that: (1) prominent pressure-broadened line wings of Na are present in the atmosphere of WASP-62b, confirming the presence of clear-sky regions; (2) a three-layer vertical temperature-pressure profile is explicitly supported, implying a significant heating process in the upper atmosphere; and (3) a significant broadening effect is detected, where the equivalent rotational velocity obtained under the assumption of a pure rotation broadening model far exceeds the rotation speed expected under the tidal-locking assumption. This study demonstrates the unique advantages of combining high- and low-resolution data for characterizing exoplanet atmospheres and provides an important reference for future detailed observations with the James Webb Space Telescope.