Supernova connection of unidentified ultra high energy gamma-ray source LHAASO J2108+5157

TL;DR

This paper proposes a phenomenological model linking supernova remnants and molecular clouds to explain the ultra high energy gamma-ray emission from LHAASO J2108+5157, suggesting SNRs can accelerate particles to PeV energies.

Contribution

The paper introduces a simple model combining hadronic and leptonic processes to explain multiwavelength observations of an unidentified gamma-ray source, emphasizing the role of old SNRs in PeV particle acceleration.

Findings

Model successfully explains the spectral energy distribution of LHAASO J2108+5157.

Supports the hypothesis that old SNRs can accelerate particles to PeV energies.

Future observations can validate the model's applicability to other sources.

Abstract

We present a simple phenomenological model of hadronic interaction between protons accelerated in an old supernova remnant (SNR) and cold protons situated within the associated molecular clouds (MCs). The accelerated protons from the old SNR escaped the SNR shock front, and got injected into the MCs at an earlier time, producing ultra high energy gamma-rays and neutrinos through inelastic proton-proton interaction. We also take into account the acceleration and subsequent escape of electrons from the SNR shock front. The escaped electrons produce gamma-rays through various radiative cooling mechanisms, after getting injected into the MCs. We use the model discussed in this letter to explain the multiwavelength (MWL) spectral energy distribution (SED) of unidentified Galactic ultra high energy gamma-ray source LHAASO J2108+5157. We also discuss the feasibility of applying this model in other cases as well. Future observations can test the viability of the model discussed in this letter, which will in turn confirm that the SNRs can, in fact, accelerate particles up to PeV energies.