Gamma-ray emission of accelerated particles escaping a supernova remnant in a molecular cloud

TL;DR

This paper develops a comprehensive model combining hydrodynamics, cosmic ray acceleration, escape, and gamma-ray emission in supernova remnants from massive stars, emphasizing the role of escaping particles interacting with surrounding dense shells.

Contribution

It introduces a new Monte Carlo method for simulating cosmic ray propagation and escape in supernova remnants, integrated into a nonlinear hydrodynamic model.

Findings

The model predicts gamma-ray emission from escaping cosmic rays interacting with dense shells.

It demonstrates the importance of particle escape in shaping the gamma-ray spectra.

The approach can be applied to various supernova types and environments.

Abstract

We present a model of gamma-ray emission from core-collapse supernovae originating from the explosions of massive young stars. The fast forward shock of the supernova remnant (SNR) can accelerate particles by diffusive shock acceleration (DSA) in a cavern blown by a strong, pre-supernova stellar wind. As a fundamental part of nonlinear DSA, some fraction of the accelerated particles escape the shock and interact with a surrounding massive dense shell producing hard photon emission. To calculate this emission, we have developed a new Monte Carlo technique for propagating the cosmic rays (CRs) produced by the forward shock of the SNR, into the dense, external material. This technique is incorporated in a hydrodynamic model of an evolving SNR which includes the nonlinear feedback of CRs on the SNR evolution, the production of escaping CRs along with those that remain trapped within the remnant, and the broad-band emission of radiation from trapped and escaping CRs. While our combined CR-hydro-escape model is quite general and applies to both core collapse and thermonuclear supernovae, the parameters we choose for our discussion here are more typical of SNRs from very massive stars whose emission spectra differ somewhat from those produced by lower mass progenitors directly interacting with a molecular cloud.