This work reports on the detection of γ-ray emission coincident with the supernova remnant (SNR) G5.7–0.1 using data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The SNR is believed to be interacting with molecular clouds, based on 1720MHz hydroxyl (OH) maser emission observations in its direction. This interaction is expected to provide targets for the pr...

The dominant background for observations of γ-rays in the energy region above 50 GeV with Imaging Atmospheric Cherenkov telescopes are cosmic-ray events. The images of most of the cosmic ray showers look significantly different from those of γ-rays and are therefore easily discriminated. However, a small fraction of events seems to be indistinguishable from γ-rays. This constitutes an irreducib...

The AGILE satellite detected several episodes of transient γ-ray emission from Cygnus X-3. Cross-correlating the AGILE light curve with both X-ray and radio monitoring data, we found that the main events of γ-ray activity were detected while the system was in soft spectral X-ray states, that coincide with local and often sharp minima of the hard X-ray flux, a few days before intense radio outbu...

We perform monthly monitoring of a sample of γ-ray blazars with the VLBA at 43 GHz along with optical photometric and polarimetric observations and 2-week campaigns (once per year) with 3 VLBA epochs during each campaign. We demonstrate that the γ-ray variability is tightly connected with the variability in the mm-wave core, especially in quasars. We show that, for all sources in our sample for...

The rapidly varying non-thermal X-ray emission observed from Sgr A⋆ points to particle acceleration taking place close to the supermassive black hole. The TeV γ-ray source HESS J1745−290 is coincident with Sgr A⋆ and may be closely related to the X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these two objects. Here we report on joint ...

Following the detection of strong TeV γ-ray flares from the BL Lac object 1ES 1959+650 with the Whipple 10 m Cherenkov telescope on May 16 and 17, 2002, we performed intensive Target of Opportunity (ToO) radio, optical, X-ray and TeV γ-ray observations from May 18, 2002 to August 14, 2002. Observations with the X-ray telescope RXTE (Rossi X-ray Timing Explorer) and the Whipple and HEGRA (High E...

RXTE, GINGA, and OSSE observations have revealed an intense low-energy γ-ray continuum emission from the Galactic plane, which is commonly interpreted as evidence for the possible existence of a strong flux of low-energy cosmic ray electrons. In this Paper I discuss the scenario of a hadronic origin of the soft Galactic γ-ray continuum through inverse bremsstrahlung. A flux of low-energy cosmic...