An Asymmetrical Model for High Energy Radiation of Cassiopeia A

TL;DR

This paper introduces an asymmetrical model for Cassiopeia A, explaining its multi-wavelength radiation through a jet-like structure and isotropic shell, and predicts high-energy gamma-ray flux detectable by future observatories.

Contribution

It presents a novel asymmetrical model combining a jet and shell to explain Cassiopeia A's radiation, including predictions for ultra-high-energy gamma-ray emission.

Findings

Model accounts for multi-wavelength spectra of Cas A.

Predicts gamma-ray flux at ~100 TeV detectable by LHAASO and CTA.

Explains the hard X-ray spectrum from 60 to 220 keV.

Abstract

Cassiopeia A (Cas A) supernova remnant shows strong radiation from radio to gamma-ray bands. The mechanism of gamma-ray radiation in Cas A and its possible contribution to PeV cosmic rays are still under debate. The X-ray imaging reveals an asymmetric profile of Cas A, suggesting the existence of a jet-like structure. In this work, we propose an asymmetrical model for Cas A, consisting of a fast moving jet-like structure and a slowly expanding isotropic shell. This model can account for the multi-wavelength spectra of Cas A, especially for the power-law hard X-ray spectrum from $\sim$ 60 to 220 keV. The GeV to TeV emission from Cas A should be contributed by both hadronic and leptonic processes. Moreover, the jet-like structure may produce a gamma-ray flux of $\sim 10^{-13}\rm erg\ cm^{-2}\ s^{-1}$ at $\sim 100$ TeV, to be examined by LHAASO and CTA.