MeV-GeV Gamma-ray Emission from SNR G327.1-1.1 Discovered by the Fermi-LAT

TL;DR

This paper reports the discovery of MeV-GeV gamma-ray emission from the supernova remnant G327.1-1.1 and its associated pulsar wind nebula, providing insights into the nebula's evolution and particle acceleration processes.

Contribution

First detection of gamma-ray emission from G327.1-1.1 with detailed multiwavelength analysis and modeling of the PWN's evolutionary stage.

Findings

Gamma-ray emission is point-like and significant (>4 sigma) in 300MeV-2TeV range.

Gamma-ray emission aligns with broadband models of an evolved PWN.

The PWN is in a late evolutionary stage with recent reverse shock interaction.

Abstract

We report the discovery of MeV-GeV gamma-ray emission by the Fermi-LAT positionally coincident with the TeV pulsar wind nebula (PWN) HESS~J1554-550 within the host supernova remnant (SNR) G327.1-1.1. The gamma-ray emission is point-like and faint but significant (> 4 sigma) in the 300MeV-2TeV energy range. We report here the Fermi-LAT analysis of the observed gamma-ray emission followed by a detailed multiwavelength investigation to understand the nature of the emission. The central pulsar powering the PWN within G327.1-1.1 has not been detected in any waveband; however, it is likely embedded within the X-ray nebula, which is displaced from the center of the radio nebula. The gamma-ray emission is faint and therefore a pulsation search to determine if the pulsar may be contributing is not feasible. Prior detailed multiwavelength reports revealed an SNR system that is old, tau ~ 18,000yrs, where the interaction of the reverse shock with the PWN is underway or has recently occurred. We find that the gamma-ray emission agrees remarkably well with a detailed broadband model constructed in a prior report based on independent hydrodynamical and semi-analytic simulations of an evolved PWN. We further investigate the physical implications of the model for the PWN evolutionary stage incorporating the new Fermi-LAT data and attempt to model the distinct particle components based on a spatial separation analysis of the displaced PWN counterparts.