Fermi Detection of the Pulsar Wind Nebula HESS J1640-465

TL;DR

This paper reports Fermi-LAT observations of the pulsar wind nebula HESS J1640-465, revealing high-energy gamma-ray emission likely originating from the nebula itself, with spectral characteristics suggesting an evolved, low-magnetic-field environment.

Contribution

It provides the first high-confidence detection of gamma-ray emission from HESS J1640-465 with Fermi-LAT and offers broadband modeling insights into its nebular properties and electron population.

Findings

Gamma-ray emission detected with high confidence.

Spectrum lacks pulsar cutoff, indicating nebula origin.

Fermi emission exceeds model predictions and has a steeper spectrum.

Abstract

We present observations of HESS J1640-465 with the Fermi-LAT. The source is detected with high confidence as an emitter of high-energy gamma-rays. The spectrum lacks any evidence for the characteristic cutoff associated with emission from pulsars, indicating that the emission arises primarily from the pulsar wind nebula. Broadband modeling implies an evolved nebula with a low magnetic field resulting in a high gamma-ray to X-ray flux ratio. The Fermi emission exceeds predictions of the broadband model, and has a steeper spectrum, possibly resulting from a distinct excess of low energy electrons similar to what is inferred for both the Vela X and Crab pulsar wind nebulae.