Fermi-LAT Gamma-ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

TL;DR

This paper reports the discovery of gamma-ray emission from a composite supernova remnant in the Large Magellanic Cloud using Fermi-LAT, suggesting an old pulsar wind nebula as the likely source.

Contribution

First detection of extragalactic PWN in the MeV-GeV band outside the Milky Way, with detailed analysis and modeling to identify the emission origin.

Findings

Gamma-ray emission detected at the SNR location with ~4 sigma significance.

The emission is unlikely from the SNR itself, pointing to a pulsar wind nebula origin.

The PWN is estimated to be about 14,000 years old, influenced by the SNR reverse shock.

Abstract

We report the second extragalactic pulsar wind nebula (PWN) to be detected in the MeV-GeV band by the Fermi-LAT, located within the Large Magellanic Cloud (LMC). The only other known PWN to emit in the Fermi band outside of the Milky Way Galaxy is N 157B which lies to the west of the newly detected gamma-ray emission at an angular distance of 4 degrees. Faint, point-like gamma-ray emission is discovered at the location of the composite supernova remnant (SNR) B0453-685 with a ~ 4 sigma significance from energies 300 MeV - 2 TeV. We present the Fermi-LAT data analysis of the new gamma-ray source, coupled with a detailed multi-wavelength investigation to understand the nature of the observed emission. Combining the observed characteristics of the SNR and the physical implications from broadband modeling, we argue it is unlikely the SNR is responsible for the gamma-ray emission. While the gamma-ray emission is too faint for a pulsation search, we try to distinguish between any pulsar and PWN component of SNR B0453-685 that would be responsible for the observed gamma-ray emission using semi-analytic models. We determine the most likely scenario is that the old PWN (t ~ 14,000 years) within B0453-685 has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below 5 GeV.