Multi-messenger observations support cosmic ray interactions surrounding acceleration sources

TL;DR

This paper combines cosmic-ray, gamma-ray, and neutrino observations to support the idea that cosmic rays interact with surrounding material near their sources, affecting their energy spectra and composition.

Contribution

It provides a multi-messenger analysis demonstrating that cosmic-ray interactions near sources contribute significantly to observed spectral features.

Findings

Cosmic-ray spectra and gamma-ray/neutrino data can be explained with a confinement time of ~0.25 Myr.

Supports the presence of significant grammage around cosmic-ray sources.

Provides evidence for source-associated interactions influencing cosmic-ray composition.

Abstract

The observations of the energy spectra of cosmic-ray have revealed complicated structures. Especially, spectral hardenings in the boron-to-carbon and boron-to-oxygen ratios above $\sim 200$ GV has been revealed by AMS-02 and DAMPE experiments. One scenario to account for the hardenings of secondary-to-primary ratios is the nuclear fragmentation of freshly accelerated particles around sources. In this work, we further study this scenario based on new observations of Galactic diffuse gamma rays by LHAASO and neutrinos by IceCube. We find that the spectra of cosmic ray nuclei, the diffuse ultra-high-energy gamma rays, and the Galactic component of neutrinos can be simultaneously explained, given an average confinement and interaction time of $\sim 0.25$ Myr around sources. These multi-messenger data thus provide evidence of non-negligible grammage of Galactic cosmic rays surrounding sources besides the traditional one during the propagation.