Activity of the Star TOI-6255 and Atmospheric Mass Loss from its Planet

We considered the planetary system of TOI-6255, in which an Earth-like planet with an extremely short period of 5.7 hours orbits an M dwarf. Based on archival measurements of TOI-6255 brightness we established rotation-induced light variability and periodic long-term variability of the object. Possible rotation period P of the star falls within the periods of 64–74 days and 78–92 days. The results were compared with those reported in the literature. For two values of logR'_HK (-5.15 and -4.66), corresponding to the peaks of the bimodal distribution of this parameter for low-activity and active M dwarfs, the atmospheric mass loss rates of the planet TOI-6255 b were estimated: 4.9 · 10⁹ g/s for logR'_HK = - 4.66, and 1.1 · 10⁹ g/s for logR'_HK = - 5.15. We determined the promise of TOI-6255 b to become a high priority subject for future research.