Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone
Munazza K. Alam, Mercedes López-Morales, Ryan J. MacDonald, Nikolay Nikolov, James Kirk, Jayesh M. Goyal, David K. Sing, Hannah R. Wakeford, Alexander D. Rathcke, Drake L. Deming, Jorge Sanz-Forcada, Nikole K. Lewis, Joanna K. Barstow, Thomas Mikal-Evans, Lars A. Buchhave
Abstract
Abstract Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise chemical abundance constraints. We present the first optical to infrared (0.3−5 μ m) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1 σ detection of Na i absorption at 0.59 μ m, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4 μ m is tentatively attributed to SiH at 2.1 σ confidence. Our retrieval analyses are consistent with a cloud-free atmosphere without significant contamination from stellar heterogeneities. We simulate James Webb Space Telescope (JWST) observations, for a combination of instrument modes, to assess the atmospheric characterization potential of WASP-62b. We demonstrate that JWST can conclusively detect Na, H 2 O, FeH, NH 3 , CO, CO 2 , CH 4 , and SiH within the scope of its Early Release Science (ERS) program. As the only transiting giant planet currently known in the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant exoplanet for detailed atmospheric characterization in the James Webb era.