New Ga IV, Ga V, Ge IV, and Ge V line widths for white dwarf spectra analysis: quantum mechanical results

Abstract

ABSTRACT We provide in this paper new Stark broadening parameters for the four ions Ga IV, Ga V, Ge IV, and Ge V. The calculations have been performed using our quantum mechanical method. To the best of our knowledge, the only available Stark broadening results are those of the Ge IV ion, where the semiclassical perturbation and the modified semi-empirical methods have been used. For the three other ions, no data have been found. In 2020 and for the first time, about five hundred lines of trans-iron elements including gallium (Ga) and germanium (Ge) have been identified in the ultraviolet (UV) spectrum of a DAO-type white dwarf BD-22°3467. Other precedent observations showed the existence of Ga IV–V lines in two white dwarfs (G191-B2B and RE 0503-289), and those of Ge IV and Ge V in the UV spectrum of RE 0503-289. Theoretical evaluations and measurements of atomic and Stark broadening data are a pre-requisite for stellar-atmosphere modelling, which is a tool for the determination of the photospheric Ga and Ge abundance in white dwarfs. Since there is no Stark broadening data for the three ions Ga IV, Ga V, and Ge V, our calculations come to fill this gap, and the obtained results can be used for the abundance determination of elements, the calculation of stellar opacity, the interpretation and modelling of stellar spectra, and the estimation of the relative transfer through stellar plasmas. They will be also implemented into the data base of Stark broadening parameters, STARK-B.