Potential PeVatron supernova remnant G106.3+2.7 seen in the highest-energy gamma rays

TL;DR

This paper reports the detection of gamma-ray emission above 10 TeV from supernova remnant G106.3+2.7, supporting its role as a PeVatron with a likely hadronic origin of the gamma rays.

Contribution

First observation of gamma rays above 10 TeV from G106.3+2.7, providing evidence for a PeVatron with a hadronic acceleration mechanism.

Findings

Gamma-ray emission detected above 10 TeV from G106.3+2.7.

Emission correlates with a molecular cloud, not the pulsar.

Supports a hadronic origin via π0 decay over leptonic mechanisms.

Abstract

Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called 'PeVatrons' inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cutoff, none of the currently known sources exhibits such a spectrum due to the low maximum energy of accelerated cosmic rays or insufficient detector sensitivity around 100 TeV. Here we report the observation of gamma-ray emission from the supernova remnant G106.3+2.7 above 10 TeV. This work provides flux data points up to and above 100 TeV and indicates that the very-high-energy gamma-ray emission above 10 TeV is well correlated with a molecular cloud rather than the pulsar PSR J2229+6114. Regarding the gamma-ray emission mechanism of G106.3+2.7, this morphological feature appears to favor a hadronic origin via the {\pi}0 decay caused by accelerated relativistic protons over a leptonic one via the inverse-Compton scattering by relativistic electrons. Furthermore, we point out that an X-ray flux upper limit on the synchrotron spectrum would provide important information to firmly establish the hadronic scenario as the mechanism of particle acceleration at the source.