A Global Perspective with Updated Constraints on the Ultra-hot Jupiter WASP-19b: Atmospheric Properties and Stellar Activity

Abstract We present a detailed reanalysis of the atmospheric properties of WASP-19b, an ultra-hot Jupiter (1.14 M Jup , 1.41 R Jup ) orbiting an active Sun-like star every 0.79 day. We reanalyze a transit and secondary eclipse of WASP-19b observed by the Hubble Space Telescope's Wide Field Camera 3 spectrograph (1.1–1.7 μ m). When combined with Spitzer photometry at longer wavelengths, our analyses indicate the presence of water absorption features in both the planet's transmission and emission spectra, consistent with results from previously published studies. We jointly fit WASP-19b’s dayside emission and transmission spectra with a retrieval model in order to constrain its atmospheric composition, and explore the effect of stellar activity on its transmission spectrum in greater depth. We also compare our dayside emission spectrum to predictions from a general circulation model, and conclude that magnetic drag appears to be relatively unimportant in shaping WASP-19b’s atmospheric circulation. Lastly, we compare the size of WASP-19b’s dayside water absorption feature to the population of hot Jupiters with similar measurements, and show that it is located in the transitional irradiation regime where temperature inversions first begin to emerge. As in previous studies, we find that the current observations provide relatively weak constraints on this planet’s atmospheric properties. These constraints could be significantly improved by the addition of spectroscopically resolved observations at longer wavelengths with JWST/NIRSpec PRISM.