Theory of stellar convection II: first stellar models

TL;DR

This paper introduces stellar models using a new scale-free convection theory (SFC) and compares its predictions with classical mixing-length theory, finding that SFC provides similar results with a more physically grounded approach.

Contribution

The paper presents the first stellar models employing the novel scale-free convection theory, demonstrating its effectiveness compared to traditional mixing-length theory.

Findings

SFC theory yields convective zones similar to ML theory for main sequence stars.

Temperature gradients and energy fluxes from SFC match classical results.

SFC theory offers a simpler, more physically grounded alternative to ML theory.

Abstract

We present here the first stellar models on the Hertzsprung-Russell diagram (HRD), in which convection is treated according to the novel scale-free convection theory (SFC theory) by Pasetto et al. (2014). The aim is to compare the results of the new theory with those from the classical, calibrated mixing-length (ML) theory to examine differences and similarities. We integrate the equations describing the structure of the atmosphere from the stellar surface down to a few percent of the stellar mass using both ML theory and SFC theory. The key temperature over pressure gradients, the energy fluxes, and the extension of the convective zones are compared in both theories. The analysis is first made for the Sun and then extended to other stars of different mass and evolutionary stage. The results are adequate: the SFC theory yields convective zones, temperature gradients of the ambient and of the convective element, and energy fluxes that are very similar to those derived from the "calibrated" MT theory for main sequence stars. We conclude that the old scale dependent ML theory can now be replaced with a self-consistent scale-free theory able to predict correct results, one which is simpler and more physically grounded than the ML theory. Fundamentally, the SFC theory offers a deeper insight of the underlying physics than numerical simulations.