Stellar laboratories IV. New Ga iv, Ga v, and Ga vi oscillator strengths and the gallium abundance in the hot white dwarfs G191−B2B and RE 0503−289

• Published in: Astronomy and astrophysics (Berlin) Vol. 577; p. A6
• Main Authors: Rauch, T, Werner, K, Quinet, P, Kruk, J W
• Format: Journal Article Web Resource
• Language: English
• Published: EDP Sciences 01.05.2015
• Subjects: Abundance; Astronomy; Mathematical models; Oscillator strengths; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; Spectra; Thermodynamic equilibrium; Ultraviolet spectra; White dwarf stars
• ISSN: 0004-6361; 1432-0746; 1432-0746
• DOI: 10.1051/0004-6361/201425326

For the spectral analysis of high-resolution and high-signal-to-noise (S/N) spectra of hot stars, advanced non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These atmospheres are strongly dependent on the reliability of the atomic data that are used to calculate them. Reliable Ga IV-VI oscillator strengths are used to identify Ga lines in the spectra of the DA-type white dwarf G191-B2B and the DO-type white dwarf RE 0503-289 and to determine their photo-spheric Ga abundances. We newly calculated Ga IV-VI oscillator strengths to consider their radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models for analyzing of Ga lines exhibited in high-resolution and high-S/N UV observations of G191-B2B and RE 0503-289. Reliable measurements and calculations of atomic data are a prerequisite for stellar-atmosphere modeling. The observed Ga IV-V line profiles in two white dwarf (G191-B2B and RE 0503-289) ultraviolet spectra were well reproduced with our newly calculated oscillator strengths. For the first time, this allowed us to determine the photo-spheric Ga abundance in white dwarfs.