Composition of Atmospheres of Normal and Peculiar stars

Context. The study of the chemical composition of stellar atmospheres is the main and most valuable source of information to determine the fundamental characteristics of stellar atmospheres, in one hand, and to studying the evolution of matter in the interior of stars, in the interstellar medium, and matter of the Galaxy, on the other hand. Aims. This study is to confirm that the effects of gravitational diffusion and light pressure begin to work, starting from specific degree of temperatures atmospheres of the main succession stars. Methods. Within the framework of this study, we processed Echelle spectra of the star “99Her” which have a spectral classes A-F, obtained with a 1.5-meter telescope PTT-150. In the investigation in question strengths of large numbers of absorption lines in stellar spectra were determined through photographic photometry of high resolution spectra, and the line strengths were than evaluated and converted into relative abundances on the basis of theoretical calculations of physical properties of model stellar atmospheres. Results. We determined the fundamental parameters of atmospheres:-the effective temperature, the acceleration of gravity, the micro-turbulent velocity. We also calculated the content of the chemical elements.