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

¹ Astronomical Observatory, Volgina 7, 11160 Belgrade 74, Serbia
² Isaac Newton Institute of Chile, Yugoslavia Branch, Yugoslavia e-mail: mdimitrijevic@aob.bg.ac.yu
³ Institute of Astronomy, Russian Academy of Science, Pyatnitskaya 48, 119017 Moscow, Russia
⁴ Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁵ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁶ Tavrian National University, Yaltinskaya 4, 330000 Simferopol, Crimea, Ukraine

Received: 5 November 2004
Accepted: 17 January 2005

Abstract

Using the semiclassical perturbation method, electron-, proton-, and ionized helium-impact line widths and shifts for the nine Cr i spectral lines from the multiplet were calculated for a perturber density of 10¹⁴ cm^-3 and for temperatures  K. The results were used to investigate the influence of Stark broadening effect in the Cr-rich Ap star β CrB atmosphere on line shapes of these lines. It was found that the contribution of proton and He ii collisions to the line width and shift is significant and comparable, and is sometimes even larger than electron-impact contribution depending of the electron temperature. Moreover, not only the Stark line width, but also the Stark shift may contribute to the blue as well as to the red asymmetry of the same line depending on the electron-, proton-, and He ii density in stellar atmosphere. The results were used to investigate the influence of Stark broadening effect on Cr i line shapes in the atmosphere of the Cr-rich Ap star  CrB.