2025A&A...699A..29S

Context. We provide structure, electron collision, and Stark broadening parameters of the Rb-like niobium ion Nb V. These data are mandatory for the spectral analysis of hot star spectra after the discovery of many lines of trans-iron elements in hot white dwarfs. To the best of our knowledge, the present results are the first to be published.
Aims. Recently, and for the first time, several lines of trans-iron elements with ionization stages IV through VII from Zn to Ba (Z = 30-56) have been discovered in the ultraviolet spectra of the atmospheres of a DAO-type white dwarf BD-22^∘3467, a DA-type white dwarf G191-B2B and a DO-type white dwarf RE 0503-289. This finding motivates us to evaluate the atomic and Stark broadening data of the Nb V ion (Z = 41), required to investigate its abundance and to interpret and analyze the observed spectra.
Methods. We used our quantum method to calculate the Stark widths. The first step of the method consisted in calculating the structure and collision parameters. In a second step, these parameters entered our codes of line broadening calculations to provide the Stark line widths. Since the accuracy of the line width results is related to the accuracy of the collision parameters, we checked the convergence of our collision results during the calculation.
Results. We provide the widths of 30 Nb V lines at different electron temperatures and at an electron density N_e = 10¹⁷ cm^–3. We compare our result with those obtained using the approximate formula of Cowley and find that rigorous calculations must be performed to obtain accurate Stark widths. We mention also that the Stark broadening mechanism is preponderant for almost all the physical conditions of the considered plasma.