Hydrodynamic simulations of the core helium flash

TL;DR

This paper presents hydrodynamic simulations of the core helium flash in a 1.25 solar mass star, confirming its quiescent nature and providing insights into convection during the event.

Contribution

It introduces a new comprehensive hydrodynamic simulation approach that supports the quiescent core helium flash scenario and enhances understanding of convection during the event.

Findings

Core helium flash remains quiescent in simulations.

Convection zone driven by helium burning is well-resolved.

Supports previous multidimensional studies of the flash.

Abstract

We describe and discuss hydrodynamic simulations of the core helium flash using an initial model of a 1.25 M_sol star with a metallicity of 0.02 near at its peak. Past research concerned with the dynamics of the core helium flash is inconclusive. Its results range from a confirmation of the standard picture, where the star remains in hydrostatic equilibrium during the flash (Deupree 1996), to a disruption or a significant mass loss of the star (Edwards 1969; Cole & Deupree 1980). However, the most recent multidimensional hydrodynamic study (Dearborn 2006) suggests a quiescent behavior of the core helium flash and seems to rule out an explosive scenario. Here we present partial results of a new comprehensive study of the core helium flash, which seem to confirm this qualitative behavior and give a better insight into operation of the convection zone powered by helium burning during the flash. The hydrodynamic evolution is followed on a computational grid in spherical coordinates using our new version of the multi-dimensional hydrodynamic code HERAKLES, which is based on a direct Eulerian implementation of the piecewise parabolic method.