We report on the investigation of a very high energy (VHE), Galactic γ-ray source recently discovered at >50 GeV using the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). This object, 2FHL J1703.4–4145, displays a very hard >50 GeV spectrum with a photon index Γ γ ∼ 1.2 in the 2FHL catalog and, as such, is one of the most extreme sources in the 2FHL subsample of Galactic objects. A detailed analysis of the available multiwavelength data shows that this source is located on the western edge of the supernova remnant (SNR) G344.7–0.1, along with extended TeV source, HESS J1702–420. The observations and the spectral energy distribution modeling support a scenario where this γ-ray source is the byproduct of the interaction between the SNR shock and the dense surrounding medium, with escaping cosmic rays (CRs) diffusing into the dense environment and interacting with a large local cloud, generating the observed TeV emission. If confirmed, an interaction between the SNR CRs and a nearby cloud would make 2FHL J1703.4–4145 another promising candidate for efficient particle acceleration of the 2FHL Galactic sample, following the first candidate from our previous investigation of a likely shock–cloud interaction occurring on the western edge of the Vela SNR.
We report the detection of gamma-ray emission from pulsar wind nebula (PWN) Kes 75 and PSR J1846−0258. Through modeling the spectral energy distribution incorporating the new Fermi-LAT data, we find that the observed gamma-ray emission is likely a combination of both the PWN and pulsar magnetosphere. The spectral shape of this magnetospheric emission is similar to the γ-ray spectrum of rotation-powered pulsars detected by Fermi-LAT, and the results from our best-fit model suggest that the pulsar’s magnetospheric emission accounts for 1% of the current spin-down luminosity. Prior works attempted to characterize the properties of this system and found a low supernova (SN) explosion energy and low SN ejecta mass. We reanalyze the broadband emission incorporating the new Fermi emission and compare the implications of our results to prior reports. The best-fit gamma-ray emission model suggests a second very hot photon field possibly generated by the stellar wind of a Wolf–Rayet star embedded within the nebula, which supports the low ejecta mass found for the progenitor in prior reports and here in the scenario of binary mass transfer.
We report on the investigation of a very high energy (VHE), Galactic γ-ray source recently discovered at >50 GeV using the Large Area Telescope (LAT) on board Fermi. This object, 2FHL J0826.1−4500, displays one of the hardest >50 GeV spectra (photon index Γ γ ∼ 1.6) in the 2FHL catalog, and a follow-up observation with XMM-Newton has uncovered diffuse, soft thermal emission at the position of the γ-ray source. A detailed analysis of the available multi-wavelength data shows that this source is located on the Western edge of the Vela supernova remnant (SNR): the observations and the spectral energy distribution modeling support a scenario where this γ-ray source is the byproduct of the interaction between the SNR shock and a neutral Hydrogen cloud. If confirmed, this shock-cloud interaction would make 2FHL J0826.1−4500 a promising candidate for efficient particle acceleration.
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