Mass Loss from the Atmosphere of the Planet WASP-193 b

Results are presented from an analysis of the manifestations of activity of the star WASP-193 of spectral class F9 with a super-neptune-type planet. The gaseous giant WASP-193 b with a mass 0.13 times Jupiter’s mass and almost one and a half times its radius. The planet has a low density ρ = 0.059±0.014 g/cm³ (Kepler 51 d is an analogous object; there are few other exoplanets of this type). The equilibrium temperature of the atmosphere of the planet is high at T_eq = 1254±31 K. The results of this study of the star’s activity are used to estimate the loss of matter by the atmosphere of the planet WASP-193 b using an approximation formula corresponding to a model with limited energy. Estimates of the flux of XUV-photons F_XUV were made using an analytical relationship relating F_XUV and the parameter ${\text{log}}{R}_{HK}{\prime}$ for stars in classes F-M. Calculations showed that the loss of matter from the atmosphere of the exoplanet is quite high (even in the case of a low chromospheric activity of the parent star). The parameter $\dot{M}$ ranges from 1.8∙10¹⁰ g/s to 4.3∙10¹¹ g/s, depending on the assumed level of the flux of XUV-photons (high and low activity). It is probable that the planet is losing its atmosphere intensively. WASP-193 b can be regarded as a high-priority candidate for observations using the JWST space mission (the transmission spectroscopy metric TSM for this object is about 600).