Warm Jupiters around M-dwarfs are great opportunities for extensive chemical, cloud and haze characterisation with JWST

Abstract: The population of short-period giant exoplanets around M-dwarf stars is slowly rising. These planets present an extraordinary opportunity for atmospheric characterisation and defy our current understanding of planetary formation. Furthermore, clouds and hazes are ubiquitous in warm exoplanets but their behaviour is still poorly understood. We study the case of a standard warm Jupiter around a M-dwarf star to show the opportunity of this exoplanet population for atmospheric characterisation. We aim to derive the cloud, haze, and chemical budget of such planets using JWST. We leverage a 3D Global Climate Model, the generic PCM, to simulate the cloudy and cloud-free atmosphere of warm Jupiters around a M-dwarf. We then post-process our simulations to produce spectral phase curves and transit spectra as would be seen with JWST.We show that using the amplitude and offset of the spectral phase curves, we can directly infer the presence of clouds and hazes in the atmosphere of such giant planets. Chemical characterisation of multiple species is possible with an unprecedented signal-to-noise ratio, using the transit spectrum in one single visit. In such atmospheres, NH3 could be detected for the first time in a giant exoplanet. We make the case that these planets are key to understanding the cloud and haze budget in warm giants. Finally, such planets are targets of great interest for Ariel.