Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid

TL;DR

This study uses 3D stellar atmosphere models from the CIFIST grid to analyze granulation properties across giants, dwarfs, and white dwarfs, revealing similar convective behaviors despite different stellar types.

Contribution

It provides a comprehensive comparison of convective processes in stars with diverse parameters using advanced 3D simulations, highlighting the universality of photospheric convection.

Findings

Intensity contrast correlates with Mach and Peclet numbers.

Granule size varies with pressure scale height and Mach number.

Convective mechanisms are similar across different stellar types.

Abstract

3D model atmospheres for giants, dwarfs, and white dwarfs, computed with the CO5BOLD code and part of the CIFIST grid, have been used for spectroscopic and asteroseismic studies. Unlike existing plane-parallel 1D structures, these simulations predict the spatially and temporally resolved emergent intensity so that granulation can be analysed, which provides insights on how convective energy transfer operates in stars. The wide range of atmospheric parameters of the CIFIST 3D simulations (3600 < Teff (K) < 13,000 and 1 < log g < 9) allows the comparison of convective processes in significantly different environments. We show that the relative intensity contrast is correlated with both the Mach and Peclet numbers in the photosphere. The horizontal size of granules varies between 3 and 10 times the local pressure scale height, with a tight correlation between the factor and the Mach number of the flow. Given that convective giants, dwarfs, and white dwarfs cover the same range of Mach and Peclet numbers, we conclude that photospheric convection operates in a very similar way in those objects.