Investigations of Optical Properties of the Atmospheres of Hot Exoplanets by Numerical Simulation of Transit Absorptions in the HeI 10 830-Å Line

— Transit observations of exoplanets make it possible to measure temperature and relative abundance of various elements in their atmospheres. The infrared line of metastable helium HeI 10 830 Å is widely used to study the atmospheres of exoplanets by the transit absorption method. The emission spectra of stars have a significant impact on the physical and chemical parameters of the upper layers of the atmospheres. In this paper, we consider the features of absorption in the helium line for stars of different spectral classes by numerical simulation. The results show the key role of the star’s emission spectrum in the formation of the upper atmosphere and in the amplitude of transit absorption of exoplanets in the HeI 10 830-Å line.