The hydrodynamics of the supernova remnant Cassiopeia A^*

The influence of the progenitor evolution on the velocity structure and clumping

¹ Astronomical Institute, Utrecht University, PO Box 80 000, 3508 TA Utrecht, The Netherlands e-mail: [b.vanveelen; n.langer; j.vink]@astro.uu.nl
² Argenlander-Institut fr Astronomie, Universitt Bonn, Auf dem Hgel 71, 53121 Bonn, Germany e-mail: nlanger@astro.uni-bonn.de
³ Instituto de Astronomía-UNAM, APDO Postal 877, Ensenada, 22800 Baja California, Mexico e-mail: ggs@astrosen.unam.mx
⁴ Centre for Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, bus 2400, 3001 Leuven, Belgium e-mail: allardjan.vanmarle@wis.kuleuven.be

Received: 27 April 2009
Accepted: 26 June 2009

Abstract

Aims. There are large differences in the proposed progenitor models for the Cas A Supernova remnant (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 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.

Methods. 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.

Results. 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 in increases shocked material. Furthermore, if a WR phase occurs, the remainders of the WR shell will be visible in the resulting SNR.

Conclusions. 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 an SN explosion taking place in a CSM that is shaped by the wind during a short (≤ 15 000 yr) WR phase, the clumps from the WR shell will be visible inside the SNR.