High-entropy ejecta plumes in Cassiopeia A from neutrino-driven convection

Abstract

Recent multi-dimensional simulations suggest that high-entropy buoyant plumes help massive stars to explode. Outwardly protruding iron-rich fingers in the galactic supernova remnant Cassiopeia A are uniquely suggestive of this picture. Detecting signatures of specific elements synthesized in the high-entropy nuclear burning regime (i.e., $\alpha$-rich freeze out) would be among the strongest substantiating evidence. Here we report the discovery of such elements, stable Ti and Cr, at a confidence level greater than 5$\sigma$ in the shocked high-velocity iron-rich ejecta of Cassiopeia A. We found the observed Ti/Fe and Cr/Fe mass ratios require $\alpha$-rich freeze out, providing the first observational demonstration for the existence of high-entropy ejecta plumes that boosted the shock wave at explosion. The metal composition of the plumes agrees well with predictions for strongly neutrino-processed proton-rich ejecta. These results support the operation of the convective supernova engine via neutrino heating in the supernova that produced Cassiopeia A.

34 pages, 13 figures

References in corpus (13)

• Theory of Core-Collapse Supernovae
• Galactic chemical evolution: Carbon through Zinc
• The Expansion Asymmetry and Age of the Cassiopeia A Supernova Remnant
• Asymmetries in core-collapse supernovae from maps of radioactive ${}^{44}$Ti in CassiopeiaA
• The distribution of radioactive ${}^{44}$Ti in Cassiopeia A
• The signature of 44Ti in Cassiopeia A revealed by IBIS/ISGRI on INTEGRAL
• Solar abundance ratios of the iron-peak elements in the Perseus Cluster
• The Bubble-like Interior of the Core-Collapse Supernova Remnant Cassiopeia A
• The Shape of Cas A
• A Comparison of X-ray and Optical Emission in Cassiopeia A
• nu-Process Nucleosynthesis in Population III Core-Collapse Supernovae
• Multi-Year X-ray Variations of Iron-K and Continuum Emissions in the Young Supernova Remnant Cassiopeia A
• Titanium and Iron in the Cassiopeia A Supernova Remnant

Cited by in corpus (2)

• Discovery of Stable Titanium at the Northeastern Jet of Cassiopeia A: Need for a Weak Jet Mechanism?
• Diagnosing The Ejecta Properties of Engine-Driven Supernovae from Observables in Their Initial Phase