Super-Knee Cosmic Rays from Galactic Neutron Star Merger Remnants

TL;DR

This paper proposes that Galactic neutron star merger remnants can accelerate heavy cosmic-ray nuclei to high energies and explain observed features in the cosmic-ray spectrum between 20 and 1000 PeV.

Contribution

It introduces a model where neutron star merger remnants significantly contribute to high-energy cosmic rays, explaining spectral features observed around 20 PeV.

Findings

NSMRs can accelerate iron nuclei up to ~500 PeV.

The model reproduces the cosmic-ray spectrum from 20 to 1000 PeV.

It explains the spectral hardening observed around 20 PeV.

Abstract

The detection of gravitational waves and electromagnetic counterparts from a binary neutron star (BNS) merger confirmed that it is accompanied by the launch of fast merger ejecta. Analogous to supernova remnants, forward shocks formed by the interaction of the ejecta with interstellar material will produce high-energy cosmic rays. We investigate the possibility that Galactic neutron star merger remnants (NSMRs) significantly contribute to the observed cosmic rays in the energy range between the knee and the ankle. Using typical parameters obtained by modeling of GW170817, we find that NSMRs can accelerate iron nuclei up to $\sim500$ PeV. We calculate the cosmic-ray spectrum and composition observed on Earth, and show that the Galactic NSMR scenario can account for the experimental cosmic-ray data in the 20 -- 1000 PeV range. Our model can naturally explain the hardening feature around 20 PeV for total cosmic-ray spectrum, which has been observed by the Telescope Array Low Energy extension and the IceTop air shower array.