3D Hydrodynamics of Pre-supernova Outbursts in Convective Red Supergiant Envelopes

TL;DR

This study uses 3D hydrodynamic simulations to investigate how convective red supergiant envelopes respond to energy deposition, revealing complex outburst dynamics and mass ejection patterns that differ from simpler models.

Contribution

It introduces 3D models of RSG envelopes showing the impact of convection on outburst behavior and mass ejection, advancing beyond previous 1D studies.

Findings

Convective motions seed instabilities, increasing ejected mass.

Density structures vary significantly with line of sight.

Outburst dynamics are heavily influenced by 3D convection.

Abstract

Eruptive mass loss likely produces the energetic outbursts observed from some massive stars before they undergo core-collapse supernovae (CCSNe). The resulting dense circumstellar medium (CSM) may also cause the subsequent SNe to be observed as Type IIn events. The leading hypothesis of the cause of these outbursts is the response of the envelope of the red supergiant (RSG) progenitor to energy deposition in the months to years prior to collapse. Early theoretical studies of this phenomena were limited to 1D, leaving the 3D convective RSG structure unaddressed. Using FLASH's hydrodynamic capabilities, we explore the 3D outcomes by constructing convective RSG envelope models and depositing energies less than the envelope binding energies on timescales shorter than the envelope dynamical time deep within them. We confirm the 1D prediction of an outward moving acoustic pulse steepening into a shock, unbinding the outermost parts of the envelope. However, we find that the initial 2-4 km/s convective motions seed the intrinsic convective instability associated with the high entropy material deep in the envelope, enabling gas from deep within the envelope to escape, increasing the amount of ejected mass compared to an initially "quiescent" envelope. The 3D models reveal a rich density structure, with column densities varying by 10x along different lines of sight. Our work highlights that the 3D convective nature of RSG envelopes impacts our ability to reliably predict the outburst dynamics, the amount, and the spatial distribution of the ejected mass associated with deep energy deposition.