The AGB bump: a calibrator for core mixing

¹ School of Physics and Astronomy, University of Birmingham, UK
² Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Aarhus, DK
³ Astrophysics Research Institute, Liverpool John Moores University, UK
⁴ INAF–Osservatorio Astronomico di Padova, Padova, IT
⁵ Dipartimento di Fisica e Astronomia, Università di Padova, Padova, IT
⁶ Scuola Internazione Superiore di Studi Avanzati SISSA, Trieste, IT
⁷ Institut d’Astrophysique et Géophysique de Université de Liège, Liège, BE

^a e-mail: dbossini@bison.ph.bham.ac.uk

Published online: 23 September 2015

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.