An extended and refined grid of 3D STAGGER model atmospheres. Processed snapshots for stellar spectroscopy - II. Giants

Title: An extended and refined grid of 3D STAGGER model atmospheres. Processed snapshots for stellar spectroscopy
Authors: Luisa F. Rodríguez Díaz, Cis Lagae, Anish M. Amarsi, Lionel Bigot, Yixiao Zhou, Víctor Aguirre Børsen-Koch, Karin Lind, Regner Trampedach, and Remo Collet

Abstract: Traditional one-dimensional hydrostatic model atmospheres introduce systematic modelling errors into spectroscopic analyses of FGK-type stars. 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. 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. 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. In conclusion, 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.

----------------------------------------------------------------------------------------------------------------------

Here we provide the dwarf model atmospheres of the stagger, with surface gravity logg >= 4.0. All models are distributed in post-processed format, meaning that the atmosphere has been reduced according to Section 4 in the paper. Original stagger models can be shared on request.

-- Instructions on how to work with the models is given in INSTRUCTIONS.

-- An overview of all the models with their stellar parameters is given in OVERVIEW

-- Example scripts to read the models, in post-processed and original format, are provided in both python and gdl. 

For the latest updates to these scripts, please refer to the github page: https://github.com/cis-lagae/STAGGER

--------------------------------------------------------------------------------
Grid Summary:
--------------------------------------------------------------------------------
 Name                Explanations
--------------------------------------------------------------------------------
ReadMe                                This file
dwarfs                                   The model files
python/post-processed   Python scripts to read the models supplied in this repository
python/stagger                  Python scripts to read the original Stagger models
gdl                                          GDL scripts to read the models supplied in this repository
convec_tables                     EOS tables to convert internal energy, density and temperature,
                                                 necessary to compute optical depth

--------------------------------------------------------------------------------
Model Summary:
--------------------------------------------------------------------------------
 FileName                Explanations
--------------------------------------------------------------------------------
atm3d.*               Atmosphere file containing the hydrodynamic variables
mesh.*                 Mesh file containing geometrical information 
info.*                    Info file containing info on the post-processing
EOSrhoe.tab      EOS table at the relevant metallicity (equal to those provide in convec_tables)
kaprhoT.tab       opacity table, used in the original stagger simulation to perform the radiative transfer