Volume 645, January 2021
|Number of page(s)||32|
|Section||Interstellar and circumstellar matter|
|Published online||14 January 2021|
The fully developed remnant of a neutrino-driven supernova
Evolution of ejecta structure and asymmetries in SNR Cassiopeia A★
INAF – Osservatorio Astronomico di Palermo,
Piazza del Parlamento 1,
2 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
3 Dip. di Fisica e Chimica, Università degli Studi di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
4 Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
5 RIKEN Interdisciplinary Theoretical & Mathematical Science Program (iTHEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Accepted: 30 November 2020
Context. The remnants of core-collapse supernovae (SNe) are probes of the physical processes associated with their parent SNe.
Aims. Here we aim to explore to which extent the remnant keeps memory of the asymmetries that develop stochastically in the neutrino-heating layer due to hydrodynamic instabilities (e.g., convective overturn and the standing accretion shock instability; SASI) during the first second after core bounce.
Methods. We coupled a three-dimensional (3D) hydrodynamic model of a neutrino-driven SN explosion, which has the potential to reproduce the observed morphology of the Cassiopeia A (Cas A) remnant, with 3D (magneto)-hydrodynamic simulations of the remnant formation. The simulations cover ≈2000 yr of expansion and include all physical processes relevant to describe the complexities in the SN evolution and the subsequent interaction of the stellar debris with the wind of the progenitor star.
Results. The interaction of large-scale asymmetries left from the earliest phases of the explosion with the reverse shock produces, at the age of ≈350 yr, an ejecta structure and a remnant morphology which are remarkably similar to those observed in Cas A. Small-scale structures in the large-scale Fe-rich plumes that were created during the initial stages of the SN, combined with hydrodynamic instabilities that develop after the passage of the reverse shock, naturally produce a pattern of ring- and crown-like structures of shocked ejecta. The consequence is a spatial inversion of the ejecta layers with Si-rich ejecta being physically interior to Fe-rich ejecta. The full-fledged remnant shows voids and cavities in the innermost unshocked ejecta, which are physically connected with ring-like features of shocked ejecta in the main shell in most cases, resulting from the expansion of Fe-rich plumes and their inflation due to the decay of radioactive species. The asymmetric distributions of 44Ti and 56Fe, which are mostly concentrated in the northern hemisphere, and pointing opposite to the kick velocity of the neutron star, as well as their abundance ratio are both compatible with those inferred from high-energy observations of Chandra and NuSTAR. Finally, the simulations show that the fingerprints of the SN can still be visible ≈2000 yr after the explosion.
Conclusions. The main asymmetries and features observed in the ejecta distribution of Cas A can be explained by the interaction of the reverse shock with the initial large-scale asymmetries that developed from stochastic processes (e.g., convective overturn and SASI activity) that originate during the first seconds of the SN blast.
Key words: hydrodynamics / instabilities / shock waves / ISM: supernova remnants / supernovae: individual: Cassiopeia A / X-rays: ISM
Movies associated to Figs. 7, 8, 12, 15 are available at https://www.aanda.org
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.