Hydrodynamic modelling of ejecta shrapnel in the Vela supernova remnant

TL;DR

This study models the evolution of ejecta shrapnel in the Vela supernova remnant using 2-D hydrodynamic simulations, highlighting the influence of initial parameters and thermal conduction on their morphology and position.

Contribution

It introduces detailed hydrodynamic simulations to understand how initial conditions and thermal effects shape ejecta clumps in the Vela SNR, providing insights into their observed structures.

Findings

Final shrapnel position is highly sensitive to initial ejecta location.

Moderately overdense knots can replicate observed detached features.

Thermal conduction causes mixing and elongation of ejecta clumps.

Abstract

Many supernova remnants (SNRs) are characterized by a knotty ejecta structure. The Vela SNR is an excellent example of remnant in which detached clumps of ejecta are visible as X-ray emitting bullets that have been observed and studied in great detail. We aim at modelling the evolution of ejecta shrapnel in the Vela SNR, investigating the role of their initial parameters (position and density) and addressing the effects of thermal conduction and radiative losses. We performed a set of 2-D hydrodynamic simulations describing the evolution of a density inhomogeneity in the ejecta profile. We explored different initial setups. We found that the final position of the shrapnel is very sensitive to its initial position within the ejecta, while the dependence on the initial density contrast is weaker. Our model also shows that moderately overdense knots can reproduce the detached features observed in the Vela SNR. Efficient thermal conduction produces detectable effects by determining an efficient mixing of the ejecta knot with the surrounding medium and shaping a characteristic elongated morphology in the clump.