HESS J1640-465 -- a Gamma-ray emitting pulsar wind nebula ?

TL;DR

This study reanalyzed eight years of Fermi LAT data for HESS J1640-465, revealing a GeV gamma-ray source consistent with a pulsar wind nebula, supporting the PWN origin over the SNR shell.

Contribution

The paper provides the first detailed GeV analysis of HESS J1640-465, demonstrating its PWN nature through spectral and morphological evidence, and connecting it with pulsar properties.

Findings

Detected extended GeV gamma-ray emission coincident with HESS J1640-465.

Spectral analysis shows a power-law with index 1.42 connecting GeV to TeV energies.

Broadband modeling supports a leptonic PWN origin for the gamma-ray emission.

Abstract

HESS J1640-465 is an extended TeV $\gamma$-ray source and its $\gamma$-ray emission whether from the shell of a supernova remnant (SNR) or a pulsar wind nebula (PWN) is still under debate. We reanalyze the GeV $\gamma$-ray data in the field of HESS J1640-465 using eight years of Pass 8 data recorded by the Fermi Large Area Telescope. An extended GeV $\gamma$-ray source positionally coincident with HESS J1640-465 is found. Its photon spectrum can be described by a power-law with an index of $1.42\pm0.19$ in the energy range of 10-500 GeV, and smoothly connects with the TeV spectrum of HESS J1640-465. The broadband spectrum of HESS J1640-465 can be well fit by a leptonic model with a broken power-law spectrum of electrons with an exponential cut-off at $\sim$ 300 TeV. The spectral properties of HESS J1640-465 are broadly consistent with the characteristics of other sources identified as PWNe, such as the correlations between high-energy luminosity ratios and the physical parameters of pulsar, including spin-down luminosity $\dot{E}$ and characteristic age $\tau_c$. All these pieces of evidence support that the $\gamma$-ray emission of HESS J1640-465 may originate from the PWN powered by PSR J1640-4631 rather than the shell of the SNR G338.3-0.0.