Explorando el impacto de los gradientes qu\'imicos en los procesos de mezcla del interior estelar

TL;DR

This paper investigates how chemical gradients influence stellar convection, proposing an extended mixing length theory that accounts for chemical instabilities, with implications for white dwarf pulsations and stellar evolution modeling.

Contribution

It introduces an extended mixing length theory incorporating chemical instabilities, improving upon standard models for stellar convection.

Findings

Extended theory predicts different chemical profiles in white dwarfs.

Comparison shows benefits of chemical instability consideration.

Impacts on pulsational mode predictions in stellar models.

Abstract

During the various steps of stellar evolution are formed convectives zones that alter the chemical stratification in stars. Usually, in astrophysics is used the Mixing Length Theory (MLT) for modeling the convective movement and, in general, it is used with the Schwarzschild instability criterion, which neglects the impact of chemical composition gradients in the development of convection. However, towards the end of central helium burning and during the thermal pulses in the Asymptotic Giant Branch (AGB) are produced stratification processes with inversions in the chemical gradient that would produce instabilities beyond the ones predicted by the Schwarzschild criterion. These instabilities would alter the chemical profile in the white dwarfs, with respect to the one predicted by MLT, having observable consequences in the pulsational modes of such objects. In the present work we will explore an extension of MLT in which we will consider the chemical instabilities as generators of convectives and non-convectives instabilities. This theory will be applied in stellar evolution models in comparison with standard MLT and a double diffusive mixing theory, discussing the benefits and shortcomings of each one.