Theoretical profiles of the Mg⁺ resonance lines perturbed by collisions with He

¹ GEPI, Observatoire de Paris, PSL Research University, UMR 8111, CNRS, Université Denis Diderot, Sorbonne Paris Cité, 61 avenue de l’Observatoire, 75014 Paris, France
e-mail: nicole.allard@obspm.fr
² Institut d’Astrophysique de Paris, UMR 7095, CNRS, Université Paris VI, 98bis boulevard Arago, 75014 Paris, France
³ Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303, CNRS, Université de Bourgogne, 21078 Dijon Cedex, France
⁴ St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia
⁵ Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky 40292, USA

Received: 23 April 2016
Accepted: 4 June 2016

Abstract

Context. The effects of collision broadening by He are central to understanding the opacity of cool stellar atmospheres.

Aims. DZ white dwarfs show metal lines which are, in many cases, believed to come from some rocky material, a remnant of a former exoplanetary system. The analysis of the Mg⁺ resonance lines is a valuable method to determine the chemical abundances in these systems.

Methods. Unified profiles of the strongest of the UV lines of Mg⁺ have been calculated in the semi-classical approach using very recent ab initio potential energies.

Results. We present the first theoretical line profile calculations of the resonance lines of Mg⁺ that have been perturbed by helium in physical conditions of atmospheres in helium-rich white dwarfs with metal traces.