Asymetrical shape of C–He lines in the ultraviolet

ABSTRACT We present the first theoretical line profile calculations of the ultraviolet spectral lines of carbon perturbed by helium using a semiclassical collision approach and high-quality ab initio potentials and electronic transition dipole moments. The temperature range is from 5000 to 8000 K. T...

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Veröffentlicht in:Monthly notices of the Royal Astronomical Society 2024-04, Vol.529 (3), p.2527-2538
Hauptverfasser: Allard, Nicole F, Spiegelman, Fernand
Format: Artikel
Sprache:eng
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Zusammenfassung:ABSTRACT We present the first theoretical line profile calculations of the ultraviolet spectral lines of carbon perturbed by helium using a semiclassical collision approach and high-quality ab initio potentials and electronic transition dipole moments. The temperature range is from 5000 to 8000 K. These results are important for astrophysical modelling of spectra in atmospheres of white dwarf stars showing atomic carbon in an helium atmosphere. Beyond the conventional symmetrical Lorentzian core at low He density, these lines exhibit a blue asymmetric behaviour. This blue asymmetry is a consequence of low maxima in the corresponding C–He potential energy difference curves at short internuclear distances. The collisional profiles are carefully examined and their perturber density dependence allow to understand the various line shapes of the observed carbon spectral lines in helium-rich white dwarf photosphere where the He perturber densities reach several 1021 cm−3.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stae477