Modelling of mercury isotope separation in CP stellar atmospheres: results and problems

TL;DR

This paper models mercury isotope separation in chemically peculiar star atmospheres using light-induced drift, highlighting the process's mechanisms, results, and the challenges in precise quantitative modeling due to data and computational demands.

Contribution

It introduces a detailed model of isotope separation via light-induced drift in CP star atmospheres, emphasizing the need for high-resolution data and computations.

Findings

LID causes heavier mercury isotopes to levitate and lighter ones to sink.

Microturbulence and stellar winds can diminish the isotope separation effect.

High-precision data and computations are essential for accurate modeling.

Abstract

Formation of anomalous isotope abundances in the atmospheres of chemically peculiar (CP) stars can be explained by light-induced drift (LID). This effect is additional to the radiative acceleration and appears due to systematic asymmetry of radiative flux in partly overlapping isotopic spectral line profiles. LID causes levitation of an isotope with a red-shifted spectral line and sinking of an isotope with a blue-shifted line, generating thus diffusive separation of isotopes. We have studied diffusion of mercury as a typical well-studied isotope-rich heavy metal. Our model computations show that in mercury-rich quiescent atmospheres of CP stars LID causes levitation of the heavier mercury isotopes and sinking of the lighter ones. Precise quantitative modelling of the process of isotope separation demands very high-resolution computations and the high-precision input data, including data on hyperfine and isotopic splitting of spectral lines, adequate line profiles and impact cross-sections. Presence of microturbulence and weak stellar winds can essentially reduce the effect of radiative-driven diffusion.