Evidence for past interaction with an asymmetric circumstellar shell in the young SNR Cassiopeia A

Understand

Observations of the SNR Cassiopeia A (Cas A) show asymmetries in the reverse shock that cannot be explained by models describing a remnant expanding through a spherically symmetric wind of the progenitor star.

• We investigate whether a past interaction of Cas A with an asymmetric circumstellar shell can account for the observed asymmetries.
• We performed 3D MHD simulations that describe the remnant evolution from the SN to its interaction with a circumstellar shell.
• The initial conditions are provided by a 3D neutrino-driven SN model whose morphology resembles Cas A.