Stark broadening of spectral lines for zirconium ions Zr iv−vi in hot white dwarf atmospheres

Abstract

ABSTRACT Stark widths for 31 spectral lines of the zirconium ions Zr iv, Zr v and Zr vi are calculated using a quantum mechanical method, and for five other lines they are deduced from a linear fit. Among these lines, 23 are provided for the first time. The motivation for this work was the recent identification of 25 lines of zirconium ions in the UV spectrum of the hot white dwarf RE 0503−289, which have never been detected before in hot white dwarfs. The results are presented for the plasma conditions found in hot white dwarf atmospheres. To the best of our knowledge, Stark broadening calculations have only been carried out for the Zr iv ion. Therefore, in addition to the quantum calculations, we perform semiclassical perturbation calculations for Zr iv lines and compare them with previous results, taking into account the effects of strong and elastic collisions on Stark broadening. Furthermore, we compare the Stark broadening with the Doppler broadening in order to ascertain their relative importance in the atmospheric conditions of DO white dwarfs. These results, together with atomic radiative data, are useful for non-local thermodynamic equilibrium stellar-atmosphere modelling.