Activity of TOI-3568 and Mass Loss of the Atmosphere of Its Exoplanet in the Sub-Jovian Desert

The properties of the TOI-3568 system, which has a super-Neptune-type planet and which by its properties falls into the region of the sub-Jovian desert, have been considered. TOI-3568 is a poorly studied dwarf of the spectral class K. Based on archival measurements of the brightness of TOI-3568 (Kamogata Wide-field Survey), the possible cyclic long-term variability of the object equal to 1.3, 1.7 and 4.1 years has been estimated. It has been found that TOI-3568 belongs to the number of old stars and can have only moderate or low activity. The mass loss from the planet’s atmosphere has been calculated using an approximation formula for the atmosphere loss model with an energy limitation. If the star is a low-activity K dwarf then $${{M}_{{{\text{loss}}}}}$$ can be $$1.18 \times {{10}^{9}}$$ g/s. If the star’s activity approaches the maximum for stars of this spectral class then the value of $${{M}_{{{\text{loss}}}}}$$ will increase in 6.3 times. Our data are in an agreement with the results characterizing the general behavior of parameter $${{M}_{{{\text{loss}}}}}$$ for other objects, including the hot Jupiter HD 189733 b and the warm Neptune GJ 436 b. The TOI-3568 system is of particular interest because it has made it possible to study rare objects located on the “mass-period” or “radius-period” diagrams of exoplanets in the region that covers the range between super-Earths and hot Jupiters (called the sub-Jovian desert) and which exhibits a deficit in the number of planets. The fact that TOI-3568 is an old star has provided a unique opportunity to trace the evolution of the properties of a planetary system currently located in the sub-Jovian desert.