TeV Electron Spectrum for Probing Cosmic-Ray Escape from a Supernova Remnant

TL;DR

This paper proposes using TeV electron spectra from supernova remnants to directly probe cosmic-ray escape processes, highlighting how energy-dependent escape shapes observable spectral features that can be detected by future experiments.

Contribution

It introduces a novel method to study cosmic-ray escape via TeV electron spectra, considering energy-dependent escape and predicting observable spectral cutoffs related to SNR age.

Findings

TeV electron spectra can reveal cosmic-ray escape features.

Low energy cutoff in spectra indicates SNR age.

Future experiments can detect these spectral features.

Abstract

One of the most essential but uncertain processes for producing cosmic-rays (CRs) and their spectra is how accelerated particles escape into the interstellar space. We propose that the CR electron spectra at >~TeV energy can provide a direct probe of the CR escape complementary to the CR nuclei and gamma-rays. We calculate the electron spectra from a young pulsar embedded in the supernova remnant (SNR), like Vela, taking into account the energy-dependent CR escape. SNRs would accelerate and hence confine particles with energy up to 10^{15.5}eV. Only energetic particles can escape first, while the lower energy particles are confined and released later. Then the observed electron spectrum should have a low energy cutoff whose position marks the age of the pulsar/SNR. The low energy cutoff is observable in the $\gtrsim {\rm TeV}$ energy window, where other contaminating sources are expected to be few due to the fast cooling of electrons. The spectrum looks similar to a dark matter annihilation line if the low energy cutoff is close to the high energy intrinsic or cooling break. The future experiments such as CALET and CTA are capable of directly detecting the CR escape features toward revealing the origin of CRs.