On the Evolution of the Maximum Energy of Accelerated Particles in Young Supernova Remnants

TL;DR

This paper investigates how the maximum energy of particles accelerated in young supernova remnants evolves, revealing it is often reached earlier than previously thought, especially in wind environments, due to detailed hydrodynamical effects.

Contribution

It provides an analytic study of particle energy evolution in SNRs, considering detailed hydrodynamics and magnetic field amplification, challenging previous assumptions about the timing of maximum energy achievement.

Findings

Maximum energy is reached during the ejecta-dominated stage.

Early maximum energy in wind-evolving supernovae.

Implications for cosmic ray acceleration in various environments.

Abstract

It has generally been assumed in the literature that while young supernova remnants (SNRs) accelerate particles even in the early stages, the particles do not escape until the start of the Sedov-Taylor or adiabatic stage, when the maximum energy of accelerated particles is reached. These calculations however do not take into account the detailed hydrodynamical expansion in the ejecta-dominated stage, and the approach to the Sedov stage. Using analytic approximations, we explore different environments in which the SNR may evolve, and investigate how the maximum energy to which particles are accelerated, and its time evolution, depends on various parameters. We take into account the ambient magnetic field and its amplification by resonant or non-resonant modes. Our studies reveal that the maximum energy to which particles are accelerated is generally reached in the ejecta-dominated stage, much before the start of Sedov stage. For SNe evolving within the winds of their massive stars, the maximum energy is reached very early in the evolution. We briefly explore the consequences for supernova remnants expanding in surroundings such as wind-bubbles or superbubbles.