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arXiv · 2110.10384

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

Toshiki Sato·Keiichi Maeda·Shigehiro Nagataki·Takashi Yoshida·Brian Grefenstette·Brian J. Williams·Hideyuki Umeda·Masaomi Ono·John P. Hughes
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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.

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Toshiki Sato, Keiichi Maeda, Shigehiro Nagataki, Takashi Yoshida, Brian Grefenstette, Brian J. Williams, Hideyuki Umeda, Masaomi Ono, John P. Hughes. 2021-10-20. High-entropy ejecta plumes in Cassiopeia A from neutrino-driven convection. https://doi.org/10.1038/s41586-021-03391-9

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