An extended and refined grid of 3D STAGGER model atmospheres

Processed snapshots for stellar spectroscopy^★

¹ Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University Ny Munkegade 120, 8000 Aarhus C, Denmark
e-mail: luisa-rodriguezdiaz@outlook.com
² Department of Astronomy, Stockholm University Albanova University Center, 106 91 Stockholm, Sweden
³ Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
⁴ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange UMR 7293, CS 34229, 06304 Nice Cedex 4, France
⁵ DARK, Niels Bohr Institute, University of Copenhagen Jagtvej 128, 2200 Copenhagen, Denmark
⁶ Space Science Institute 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA

Received: 2 November 2023
Accepted: 13 May 2024

Abstract

Context. Traditional one-dimensional hydrostatic model atmospheres introduce systematic modelling errors into spectroscopic analyses of FGK-type stars.

Aims. We present an updated version of the STAGGER-grid of three-dimensional model atmospheres, and explore the accuracy of postprocessing methods in preparation for spectral synthesis.

Methods. New and old models were (re)computed following an updated workflow, including an updated opacity binning technique. Spectroscopic tests were performed in three-dimensional local thermodynamic equilibrium for a grid of 216 fictitious Fe I lines, spanning a wide range of oscillator strengths, excitation potentials, and central wavelengths, and eight model atmospheres that cover the stellar atmospheric parameter range (T_eff, log g, and [Fe/H]) of FGK-type stars. Using this grid, the impact of vertical and horizontal resolutions, and temporal sampling of model atmospheres on spectroscopic diagnostics, was tested.

Results. We find that downsampling the horizontal mesh from its original size of 240 × 240 grid cells to 80 × 80 cells, in other words, sampling every third grid cell, introduces minimal errors on the equivalent width and normalised line flux across the line and stellar parameter space. Regarding temporal sampling, we find that sampling ten statistically independent snapshots is sufficient to accurately model the shape of spectral line profiles. For equivalent widths, a subsample consisting of only two snapshots is sufficient, introducing an abundance error of less than 0.015 dex.

Conclusions. We have computed 32 new model atmospheres and recomputed 116 old ones present in the original grid. The public release of the STAGGER-grid contains 243 models and the processed snapshots can be used to improve the accuracy of spectroscopic analyses.