Lepto-Hadronic Origin of gamma-rays from the G54.1+0.3 Pulsar Wind Nebula

TL;DR

This paper models the gamma-ray emission from the G54.1+0.3 pulsar wind nebula, demonstrating that a lepto-hadronic hybrid model explains the observed spectrum better than leptonic models alone, with proton interactions playing a key role.

Contribution

It introduces a lepto-hadronic hybrid model for the PWN's gamma-ray emission, incorporating proton interactions with surrounding material, which better fits the observed data.

Findings

TeV gamma-rays mainly from π^0 decay in proton-proton interactions.

Leptonic models alone cannot reproduce the observed spectrum.

Infrared loop and molecular cloud serve as targets for proton bombardment.

Abstract

G54.1+0.3 is a Crab-like pulsar wind nebula (PWN) with the highest $\gamma$-ray to X-ray luminosity ratio among all the nebulae driven by young rotation-powered pulsars. We model the spectral evolution of the PWN and find it difficult to match the observed multi-band data with leptons alone using reasonable model parameters. In lepton-hadron hybrid model instead, TeV photons come mainly from $\pi^0$ decay in proton-proton interaction and the observed photon spectrum can be well reproduced. The newly discovered infrared loop and molecular cloud in or closely around the PWN can work as the target for the bombardment of the PWN protons.