HESS J1640-465 - an exceptionally luminous TeV gamma-ray supernova remnant

The results of follow-up observations of the TeV γ-ray source HESS J1640−465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well described by an exponential cut-off power law with photon index Γ = 2.11 ± 0.09stat ± 0.10sys, and a cut-off energy of Ec=6.0+2.0−1.2 TeV. The TeV emission is significantly extended and overlaps with the northwestern part of the shell of the SNR G338.3−0.0. The new HESS results, a re-analysis of archival XMM-Newton data and multiwavelength observations suggest that a significant part of the γ-ray emission from HESS J1640−465 originates in the supernova remnant shell. In a hadronic scenario, as suggested by the smooth connection of the GeV and TeV spectra, the product of total proton energy and mean target density could be as high as WpnH ∼ 4 × 1052(d/10kpc)2 erg cm−3.