The acceleration of cosmic-ray protons in the supernova remnant RX J1713.7-3946

TL;DR

This paper provides evidence that supernova remnant RX J1713.7-3946 accelerates cosmic-ray protons to very high energies, confirmed by gamma-ray observations matching pion decay signatures.

Contribution

It presents observational evidence linking supernova remnant shock waves to proton acceleration via gamma-ray spectral analysis, supporting the hadronic acceleration model.

Findings

Gamma-ray spectrum matches pion decay predictions

Protons are accelerated up to 10^15 eV in the remnant

Supports supernova remnants as sources of high-energy cosmic rays

Abstract

Protons with energies up to 10^15 eV are the main component[1] of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking[2]. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants[3, 4], and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi0), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in g-rays with a particular spectral-energy distribution[5, 6]. Here we report the observation of cascade showers of optical photons resulting fromg-rays at energies of 10^12 eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.