Discovery of a VHE gamma-ray source coincident with the supernova remnant CTB 37A

Aims. The supernova remnant (SNR) complex CTB 37 is an interesting candidate for observations with very high energy (VHE) $\gamma$-ray telescopes such as HESS. In this region, three SNRs are seen. One of them is potentially associated with several molecular clouds, a circumstance that can be used to probe the acceleration of hadronic cosmic rays. Methods. This region was observed with the HESS Cherenkov telescopes and the data were analyzed with standard HESS procedures. Recent X-ray observations with Chandra and XMM-Newton were used to search for X-ray counterparts. Results. The discovery of a new VHE $\gamma$-ray source HESS J1714-385 coincident with the remnant CTB 37A is reported. The energy spectrum is well described by a power-law with a photon index of $\Gamma$ = 2.30 $\pm$ 0.13 and a differential flux at 1 TeV of $\Phi_0 = (8.7 \pm 1.0_{\mathrm{stat}} \pm 1.8_{\mathrm{sys}}) \times 10^{-13}$ cm-2 s-1 TeV-1. The integrated flux above 1 TeV is equivalent to 3% of the flux of the Crab nebula above the same energy. This VHE $\gamma$-ray source is a counterpart candidate for the unidentified EGRET source 3EG J1714-3857. The observed VHE emission is consistent with the molecular gas distribution around CTB 37A; a close match is expected in a hadronic scenario for $\gamma$-ray production. The X-ray observations reveal the presence of thermal X-rays from the NE part of the SNR. In the NW part of the remnant, an extended non-thermal X-ray source, CXOU J171419.8-383023, is discovered as well. Possible connections of the X-ray emission to the newly found VHE source are discussed

Discovery of VHE gamma-rays from the distant BL Lacertae 1ES0347-121

Aims.Our aim is to study the production mechanism for very-high-energy (VHE; >100 GeV) $\gamma$-rays in distant active galactic nuclei (AGN) and use the observed VHE spectrum to derive limits on the Extragalactic Background Light (EBL). We also want to determine physical quantities through the modeling of the object's broad-band spectral energy distribution (SED). Methods.VHE observations (~25 h live time) of the BL Lac 1ES 0347-121 (redshift z = 0.188) were conducted with the High Energy Stereoscopic System (HESS) between August and December 2006. Contemporaneous X-ray and UV/optical observations from the SWIFT satellite are used to interpret the SED of the source in terms of a synchrotron self Compton (SSC) model. Results.An excess of 327 events, corresponding to a statistical significance of 10.1 standard deviations, is detected from 1ES 0347-121. Its photon spectrum, ranging from ~250 GeV to ~3 TeV, is well described by a power law with a photon index of $\Gamma = 3.10 \pm 0.23_{\mathrm{stat}} \pm 0.10_{\mathrm{sys}}$. The integral flux above 250 GeV corresponds to ~2% of the flux of the Crab Nebula above the same threshold. No VHE flux variability is detected within the data set. Conclusions.Constraints on the EBL density at optical to near-infrared wavelengths derived from the photon spectrum of 1ES 0347-121 are close to the strongest limits derived previously. The strong EBL limits confirm earlier findings, that the EBL density in the near-infrared is close to the lower limits from source counts. This implies that the universe is more transparent to VHE $\gamma$-rays than previously believed. An SSC model provides a reasonable description of the contemporaneous SED