Oxygen spectral line synthesis: 3D non-LTE with CO5BOLD hydrodynamical model atmospheres

TL;DR

This paper presents the first 3D non-LTE spectral synthesis of the solar oxygen IR triplet using hydrodynamical models, showing that NLTE effects deepen the line cores and impact abundance estimates.

Contribution

It introduces a combined 3D hydrodynamical and non-LTE spectral synthesis approach for oxygen lines in stellar atmospheres, improving physical realism.

Findings

NLTE lines are deeper, indicating stronger lines in NLTE conditions.

Negative 3D NLTE-LTE abundance corrections suggest lower solar oxygen abundance.

Supports previous claims of a relatively low solar oxygen abundance.

Abstract

In this work we present first results of our current project aimed at combining the 3D hydrodynamical stellar atmosphere approach with non-LTE (NLTE) spectral line synthesis for a number of key chemical species. We carried out a full 3D-NLTE spectrum synthesis of the oxygen IR 777 nm triplet, using a modified and improved version of our NLTE3D package to calculate departure coefficients for the atomic levels of oxygen in a CO5BOLD 3D hydrodynamical solar model atmosphere. Spectral line synthesis was subsequently performed with the Linfor 3D code. In agreement with previous studies, we find that the lines of the oxygen triplet produce deeper cores under NLTE conditions, due to the diminished line source function in the line forming region. This means that the solar oxygen IR 777 nm lines should be stronger in NLTE, leading to negative 3D NLTE-LTE abundance corrections. Qualitatively this result would support previous claims for a relatively low solar oxygen abundance. Finally, we outline several further steps that need to be taken in order to improve the physical realism and numerical accuracy of our current 3D-NLTE calculations.