Impact of central mixing scheme and nuclear reaction network on the extent of convective cores

Abstract

Convective cores are the hydrogen reservoirs of main sequence stars that are more massive than around 1.2 solar masses. The characteristics of the cores have a strong impact on the evolution and structure of the star. However, such results rely on stellar evolution codes, in which simplistic assumptions are often made on the physics in the core. Indeed, mixing is commonly considered to be instantaneous and the most basic nuclear networks assume beryllium at its equilibrium abundance. Those assumptions lead to significant differences in the central composition of the elements for which the timescale to reach nuclear equilibrium is lower than the convective timescale. In this work, we show that those discrepancies impact the nuclear energy production and, therefore, the size of convective cores in models computed with overshoot. We find that cores computed with instantaneous mixing are up to 30% bigger than those computed with diffusive mixing. Similar differences are found when using basic nuclear networks. Additionally, we observed an extension of the duration of the main sequence due to those core size differences. We then investigated the impact of those structural differences on the seismic modeling of solar-like oscillators. Modeling two stars observed by Kepler, we find that the overshoot parameter of the best models computed with a basic nuclear network is significantly lower, compared to models computed with a full nuclear network. This work is a necessary step in improving the modeling of convective cores, which is key to determining accurate ages in the framework of future space missions such as Plato.

10 pages, 11 figures, accepted in A&A. Second version changes title and corrects language

References in corpus (14)

• Modules for Experiments in Stellar Astrophysics (MESA)
• ADIPLS -- the Aarhus adiabatic oscillation package
• ASTEC -- the Aarhus STellar Evolution Code
• Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters
• Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars
• CLES, Code Liegeois d'Evolution Stellaire
• CESAM: a free code for stellar evolution calculations
• Internal mixing of rotating stars inferred from dipole gravity modes
• Asteroseismic masses, ages, and core properties of $\gamma$ Doradus stars using gravito-inertial dipole modes and spectroscopy
• Constraining stellar evolution theory with asteroseismology of $\gamma$ Doradus stars using deep learning
• Convective core entrainment in 1D main sequence stellar models
• CoRoT/ESTA-TASK 1 and TASK 3 comparison of the internal structure and seismic properties of representative stellar models: Comparisons between the ASTEC, CESAM, CLES, GARSTEC and STAROX codes
• Probing core overshooting using subgiant asteroseismology: the case of KIC10273246
• Core overshoot constrained by the absence of a solar convective core and some solar-like stars

Cited by in corpus (4)

• Asteroseismology of the young open cluster NGC 2516 II. Constraining cluster age using gravity-mode pulsators
• Asteroseismic Structure Inversions of Main-Sequence Solar-like Oscillators with Convective Cores
• Detailed theoretical analysis of core Helium-burning stars: Mixed mode patterns I. Impact of the He-flash discontinuity and of induced semi-convection
• Ensemble seismic study of the properties of the core of Red Clump stars