The hydrodynamics of the supernova remnant Cas A: The influence of the progenitor evolution on the velocity structure and clumping

TL;DR

This study uses hydrodynamical simulations to explore how the progenitor star's Wolf-Rayet phase influences the structure and velocity profile of the Cas A supernova remnant, suggesting the star likely did not undergo a WR phase.

Contribution

The paper provides the first detailed hydrodynamical modeling to assess the impact of the progenitor's WR phase duration on the SNR's features, linking simulations with observations.

Findings

Progenitor of Cas A likely did not have a WR phase.

Longer WR phases decrease reverse shock velocities and increase velocity range.

Observed features are inconsistent with a WR shell origin.

Abstract

There are large differences in the proposed progenitor models for the Cas A SNR. One of these differences is the presence or absence of a Wolf-Rayet (WR) phase of the progenitor star. The mass loss history of the progenitor star strongly affects the shape of the Supernova remnant (SNR). In this paper we investigate whether the progenitor star of Cas A had a WR phase or not and how long it may have lasted. We performed two-dimensional multi-species hydrodynamical simulations of the CSM around the progenitor star for several WR life times, each followed by the interaction of the supernova ejecta with the CSM. We then looked at the influence of the length of the WR phase and compared the results of the simulations with the observations of Cas A. The difference in the structure of the CSM, for models with different WR life times, has a strong impact on the resulting SNR. With an increasing WR life time the reverse shock velocity of the SNR decreases and the range of observed velocities in the shocked material increases. Furthermore, if a WR phase occurs, the remainders of the WR shell will be visible in the resulting SNR. Comparing our results with the observations suggests that the progenitor star of Cas A did not have a WR phase. We also find that the quasi-stationary flocculi (QSF) in Cas A are not consistent with the clumps from a WR shell that have been shocked and accelerated by the interaction with the SN ejecta. We can also conclude that for a SN explosion taking place in a CSM that is shaped by the wind during a short < 15000 yr WR phase, the clumps from the WR shell will be visible inside the SNR.