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The elemental energy spectra of cosmic rays play an important role in understanding their acceleration and propagation. Most current results are obtained either from direct measurements by balloon or satellite detectors, or from indirect…
We present the first catalogs of the highest-energy (above 56 TeV and 100 TeV) gamma-ray sources seen by the High Altitude Water Cherenkov (HAWC) Observatory. The wide field-of-view of HAWC naturally lends itself to unbiased all-sky surveys…
The VERITAS gamma-ray observatory, situated in southern Arizona, is an array of four 12m diameter imaging Cherenkov telescopes, each with a 499-pixel photomultiplier-tube camera. The instrument is designed to detect astrophysical gamma rays…
VERITAS is the high-sensitivity instrument of latest generation. It is often used for the short AGN monitoring exposures evenly distributed over entire observational season of a source of interest. Each of these exposures is long enough to…
Telescopes based on the imaging atmospheric Cherenkov technique (IACTs) detect images of the atmospheric showers generated by gamma rays and cosmic rays as they are absorbed by the atmosphere. The much more frequent cosmic-ray events form…
Geminga was first detected as a gamma-ray point source by the SAS-2 gamma-ray satellite observatory and the COS-B X-ray satellite observatory. Subsequent observations have identified Geminga as a heavily obscured radio-quiet pulsar…
Stereoscopic viewing of TeV gamma-ray air showers with systems of Imaging Atmospheric Cherenkov Telescopes (IACTs) allows to reconstruct the origin of individual primary particles with an accuracy of 0.1 degree or better. The shower impact…
The Cygnus region of the galaxy is one of the richest regions of gas and star formation and is the brightest region of diffuse GeV emission in the northern sky. VERITAS has conducted deep observations (approximately 300 hours) in the…
The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring in Active Galactic Nuclei from radio waves to TeV gamma-rays. Here we report the detection of gamma-ray…
As TeV gamma-ray astronomy progresses into the era of the Cherenkov Telescope Array (CTA), instantaneously following up on gamma-ray transients is becoming more important than ever. To this end, a worldwide network of Imaging Atmospheric…
Many of the recently discovered galactic very high-energy (VHE) gamma-ray sources are associated with Pulsar Wind Nebulae, which is the most populous Galactic source category at TeV energies. The extended synchrotron nebulae of these…
The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV--100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this reason, VHE gamma rays are…
The reflector used by an imaging atmospheric Cherenkov telescope (IACT) consists of a tessellated array of mirrors mounted on a large frame. This arrangement allows for a very large reflecting surface with sufficient optical quality for the…
The study of $\gamma$-ray emission from galactic sources such as supernova remnants (SNR) may provide key insights into their potential role as accelerators of cosmic rays up to the knee ($\sim 10^{15}$ eV). The VERITAS Observatory is…
The Cherenkov Telescope Array (CTA) will be the next-generation gamma-ray observatory, investigating gamma-ray and cosmic ray astrophysics at energies from 20 GeV to more than 300 TeV. The observatory, consisting of large arrays of imaging…
The recent detection of 12 gamma-ray Galactic sources well above E > 100 TeV by the LHAASO observatory has been a breakthrough in the context of Cosmic Ray (CR) origin search. Although most of these sources are unidentified, they are often…
The Imaging Atmospheric Cherenkov technique allows to detect very high energy gamma rays from few tens of GeV to hundreds of TeV using ground-based instrumentation. At these energies a gamma ray generates a shower of secondary particles…
The High Altitude Water Cherenkov Observatory (HAWC) has a wide field-of-view (FOV, $\sim$2sr) and a high duty cycle ($\sim$95\%), which make it a powerful survey and monitoring experiment for sources of TeV gamma rays. We present a…
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is carrying out a detailed survey of the northern sky at TeV energies. 2HWC J2006+341 is a newly discovered source reported by the point source search in the 2HWC HAWC…
We present a procedure to optimize the offset angle (usually also known as the wobble distance) and the signal integration region for the observations and analysis of extended sources by Imaging Atmospheric Cherenkov Telescopes (IACTs) such…