Constraining the origin of the puzzling source HESS J1640-465 and the PeVatron candidate HESS J1641-463 using Fermi-LAT observations

Abstract

There are only few very-high-energy sources in our Galaxy which might accelerate particles up to the knee of the cosmic-ray spectrum. To understand the mechanisms of particle acceleration in these PeVatron candidates, \textit{Fermi}-LAT and H.E.S.S. observations are essential to characterize their $\gamma$-ray emission. HESS J1640$-$465 and the PeVatron candidate HESS J1641$-$463 are two neighboring (\ang[astroang]{0.25}) $\gamma$-ray sources, spatially coincident with the radio supernova remnants (SNRs) G338.3$-$0.0 and G338.5+0.1. Detected both by H.E.S.S. and \textit{Fermi}-LAT, we present here a morphological and spectral analysis of these two sources using 8 years of \textit{Fermi}-LAT data between 200 \si{\mega\electronvolt} and 1 \si{\tera\electronvolt} with multi-wavelength observations to assess their nature. The morphology of HESS J1640$-$465 is described by a 2D Gaussian ($\sigma =$ \ang[astroang]{0.053} $\pm$ \ang[astroang]{0.011}${}_{stat}$ $\pm$ \ang[astroang]{0.03}${}_{syst}$) and its spectrum is modeled by a power-law with a spectral index $\Gamma =1.8\pm 0.1_{\mathrm{stat}}\pm 0.2_{\mathrm{syst}}$. HESS J1641$-$463 is detected as a point-like source and its GeV emission is described by a logarithmic-parabola spectrum with $\alpha =2.7\pm 0.1_{\mathrm{stat}}\pm 0.2_{\mathrm{syst}}$ and significant curvature of $\beta =0.11\pm 0.03_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}}$. Radio and X-ray flux upper limits were derived. We investigated scenarios to explain their emission, namely the emission from accelerated particles within the SNRs spatially coincident with each source, molecular clouds illuminated by cosmic rays from the close-by SNRs, and a pulsar/PWN origin. Our new \emph{Fermi}-LAT results and the radio and flux X-ray upper limits pose severe constraints on some of these models.

18 pages 7 figures To be published in ApJ

References in corpus (17)

• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope
• A Dynamical Model for the Evolution of a Pulsar Wind Nebula inside a Non-Radiative Supernova Remnant
• Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field
• The Southern Galactic Plane Survey: Polarized Radio Continuum Observations and Analysis
• Hadronic gamma-rays from RX J1713.7-3946?
• In which shell-type SNRs should we look for gamma-rays and neutrinos from p-p collisions?
• The distance and neutral environment of the massive stellar cluster Westerlund 1
• The Einstein@Home Gamma-ray Pulsar Survey. I. Search Methods, Sensitivity and Discovery of New Young Gamma-ray Pulsars
• NuSTAR Discovery of a Young, Energetic Pulsar Associated with the Luminous Gamma-ray Source HESS J1640-465
• XMM-Newton observations reveal the X-ray counterpart of the very-high-energy gamma-ray source HESSJ1640-465
• Discovery of the hard spectrum VHE gamma-ray source HESS J1641-463
• The Galactic population and properties of young, highly-energetic pulsars
• Optimized Blind Gamma-ray Pulsar Searches at Fixed Computing Budget
• Interstellar gas towards the TeV gamma-ray sources HESS J1640-465 and HESS J1641-463
• Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources
• HESS J1640-465 and HESS J1641-463: two intriguing TeV sources in the light of new Fermi LAT observations

Cited by in corpus (4)

• Incremental Fermi Large Area Telescope Fourth Source Catalog
• Study of maximum electron energy of sub-PeV pulsar wind nebulae by multiwavelength modelling
• Broadband X-ray Spectroscopy of the Pulsar Wind Nebula in HESS J1640-465
• Fermi-LAT Gamma-ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud