On the influence of Stark broadening on Si I lines in stellar atmospheres

We study the influence of Stark broadening and stratification effects on Si I lines in the rapidly oscillating (roAp) star 10 Aql, where the Si I 6142.48 (angstrom)and 6155.13 (angstrom)lines are asymmetrical and shifted. First we have calculated Stark broadening parameters using the semiclassical perturbation method for three Si I lines: 5950.2 (angstrom), 6142.48 (angstrom)and 6155.13 (angstrom). We revised the synthetic spectrum calculation code taking into account both Stark width and shift for these lines. From the comparison of our calculations with the observations we found that Stark broadening + the stratification effect can explain asymmetry of the Si I 6142.48 (angstrom) and 6155.13 (angstrom) lines in the atmospere of roAp star 10 Aql.