The AGB bump: a calibrator for the core mixing

TL;DR

This paper investigates how different assumptions about near-core mixing and thermal stratification influence the luminosity of the AGB bump and gravity mode period spacing, providing a potential calibration tool for stellar core mixing models.

Contribution

It introduces a method to use the AGB bump luminosity as a calibrator for core mixing efficiency in stellar models.

Findings

Different mixing assumptions significantly affect AGB bump luminosity.

Thermal stratification impacts gravity mode period spacing.

The AGB bump can serve as a calibration for core mixing models.

Abstract

The efficiency of convection in stars affects many aspects of their evolution and remains one of the key-open questions in stellar modelling. In particular, the size of the mixed core in core-He-burning low-mass stars is still uncertain and impacts the lifetime of this evolutionary phase and, e.g., the C/O profile in white dwarfs. One of the known observables related to the Horizontal Branch (HB) and Asymptotic Giant Branch (AGB) evolution is the AGB bump. Its luminosity depends on the position in mass of the helium-burning shell at its first ignition, that is affected by the extension of the central mixed region. In this preliminary work we show how various assumptions on near-core mixing and on the thermal stratification in the overshooting region affect the luminosity of the AGB bump, as well as the period spacing of gravity modes in core-He-burning models.