Cesam2k20: A code for a new generation of stellar evolution models. I. Description of the code

TL;DR

Cesam2k20 is a modern, publicly available stellar evolution code that incorporates advanced models for chemical and angular momentum transport, validated through extensive testing and used for stellar modeling in the PLATO mission.

Contribution

It introduces Cesam2k20, a new version of the stellar evolution code with improved physical process modeling and a unique numerical approach, enhancing accuracy and usability.

Findings

Implementation of state-of-the-art transport models

Validation against other stellar evolution codes

Application to solar models demonstrating improvements

Abstract

We present Cesam2k20, the latest version of the hydrostatic stellar evolution code CESAM originally developed by P. Morel and collaborators. Over the last three decades, it has undergone many improvements and has been extensively tested against other stellar evolution codes before being selected to compute the first-generation grid of stellar models for the PLATO mission. Among all the developments made thus far, Cesam2k20 now implements state-of-the-art models for the transport of chemical elements and angular momentum. It was recently made publicly available with an ecosystem of other codes interfaced with it: 1D and 2D oscillation codes ADIPLS and ACOR, optimisation program OSM, and Python utility package pycesam. This paper recalls the numerical peculiarities of Cesam2k20, namely, the use of a collocation method where the structure variables are decomposed as piecewise polynomials projected on a B-spline basis. Here, we review the options available for modelling the different physical processes. In particular, we illustrate the improvements made in the transport of chemical elements and angular momentum with a series of standard and non-standard solar models.