Related papers: Highlights from the VERITAS AGN Observation Progra…
The Very High Energy Radiation Telescope Array (VERITAS) is a system of four imaging Cherenkov telescopes currently under construction at Kitt Peak, Arizona, USA. The first telescope has been in operation at the Mt. Hopkins basecamp since…
The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E > 100 GeV) part of its broadband spectrum particularly interesting,…
In the recent years, the new generation of Imaging Atmospheric Cerenkov Telescopes successfully detected very high energy (VHE; E>100 GeV) gamma-ray emission from a growing number of Active Galactic Nuclei (AGNs), mainly belonging to the…
The four-year X-ray all-sky survey (eRASS) of the eROSITA telescope aboard the Spektrum-Roentgen-Gamma satellite will detect ~3 million active galactic nuclei (AGN) with a median redshift of z~1 and a typical luminosity of L_(0.5-2.0 keV) ~…
The ground-based EAS array is usually operated with a high duty cycle (> 90%) and a large field of view (~2 sr), which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-ray emission mechanism and…
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…
VERITAS employs a 12m segmented mirror and pixellated photomultiplier tube camera to detect the brief pulse of Cherenkov radiation produced by the extensive air shower initiated by a cosmic high-energy gamma ray. The VERITAS data…
Active galactic nuclei (AGN) are a promising source for high-energy astrophysical neutrinos (HEANs). By the end of 2022, the Vera C. Rubin Observatory (VRO) will begin to observe $\gtrsim10$ million AGN with a regular and high cadence.…
As a critical part of the Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) program, in November 2007 the Australia Telescope Compact Array (ATCA) started monitoring the radio spectra of a sample of…
The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based array located at the Fred Lawrence Whipple Observatory in southern Arizona and is one of the world's most sensitive gamma-ray instruments at energies of…
Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged as the most sensitive gamma-ray detectors in the energy range of about 100 GeV and above. The strengths of these arrays are a very large effective collection area…
The Cherenkov Telescope Array (CTA), currently in its Preparatory Phase, will be the first open observatory for very high energy gamma-rays from galactic and extragalactic sources. The international consortium behind CTA is preparing the…
It is notoriously difficult to organize simultaneous observations from space and from the ground. This is particularly so at GeV-TeV energies where the space observations from all sky telescopes and the ground-based observations (mostly…
We present long-term observations of several VHE (E > 100 GeV) blazars with VERITAS, together with contemporaneous Swift and RXTE X-ray data. The observed targets include Mrk 421, Mrk 501, 1ES 2344+514. Strong flux and spectral variability…
X-ray selected BL Lac objects dominate the population of extragalactic sources detected in the very high energy (VHE; photon energies >100GeV) gamma-ray regime with ground-based Cherenkov Telescopes. These are not the only extragalactic VHE…
Imaging Atmospheric Cherenkov Telescopes have long been viewed as potential light collectors to be used for long baseline optical intensity interferometry observations. Intensity interferometry, as implemented with Cherenkov telescopes, is…
The VERITAS IACT observatory has carried out an extensive survey of the Cygnus region between 67 and 82 degrees in galactic longitude and between -1 and 4 degrees in galactic latitude. This region is a natural choice for a Very High Energy…
We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the VERITAS array of Cherenkov telescopes. 1ES 0414+009 was observed by VERITAS between January 2008 and February 2011, resulting in 56.2 hours of…
During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, $E>100$ GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background…
In any given 24-hour period, the Fermi-LAT detects photons with energies of order 100 GeV not associated with any known VHE emitter. The RA/Dec of these photons frequently falls into the field of view of VERITAS the following evening. A…