Non-LTE Radiative Transfer with Turbospectrum

TL;DR

This paper introduces an updated version of the Turbospectrum code capable of NLTE spectrum synthesis, improving the modeling of stellar spectra for various astrophysical applications.

Contribution

The paper presents a new NLTE extension of Turbospectrum, enabling more realistic stellar spectrum modeling with publicly available microphysics data and departure coefficient grids.

Findings

NLTE models better fit observed stellar spectra.

Enhanced accuracy in metallicity and abundance determinations.

Public release of code and microphysics data.

Abstract

Physically realistic models of stellar spectra are needed in a variety of astronomical studies, from the analysis of fundamental stellar parameters, to studies of exoplanets and stellar populations in galaxies. Here we present a new version of the widely-used radiative transfer code Turbospectrum, which we update with the capacity to perform spectrum synthesis for lines of multiple chemical elements in Non-Local Thermodynamic Equilibrium (NLTE). We use the code in the analysis of metallicites and abundances of the Gaia FGK benchmark stars, using one-dimensional MARCS atmospheric models and the averages of 3D radiation-hydrodynamics simulations of stellar surface convection. We show that the new more physically realistic models offer a better description of the observed data and make the program and the associated microphysics data publicly available, including grids of NLTE departure coefficients for H, O, Na, Mg, Si, Ca, Ti, Mn, Fe, Co, Ni, Sr, and Ba.