Related papers: Optical spectroscopy of blazars for the Cherenkov …
The VERITAS array of 12-m atmospheric-Cherenkov telescopes is used in an intensive observation program focused on the discovery of VHE (E > 100 GeV) gamma-ray-emitting blazars. Since VERITAS began full-scale operation in 2007, more than…
Context. We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155-304, W Comae, and of the flat spectrum radio quasar PKS 1510-089, as a part of a photometric monitoring program in the…
We present the results of a multi-wavelength study of blazars selected from the 5th ROMABZCAT catalog. We selected from this sample a subsample of 2435 objects having at least one counterpart in one of the three main archival X-ray…
The Cherenkov Telescope Array (CTA) will be able to perform unprecedented observations of the transient very high-energy sky. An on-line science alert generation (SAG) pipeline, with a required 30 second latency, will allow the discovery or…
The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar…
For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory…
The uncharted territory of the high-redshift ($z\gtrsim3$) Universe holds the key to understand the evolution of quasars. In an attempt to identify the most extreme members of the quasar population, i.e., blazars, we have carried out a…
Blazars, one of the most extreme class of active galaxies, constitute so far the largest known population of $\gamma$-ray sources and their number is continuously growing in the Fermi catalogs. However in the latest release of the Fermi…
High-$z$ blazars (z $\geq 2.5$) are the most powerful class of persistent $\gamma$-ray sources in the Universe. These objects possess the highest jet powers and luminosities and have black hole masses often in excess of $10^9$ solar masses.…
We report on HET and Palomar 5 m spectroscopy of recently identified $\gamma$-ray blazars in the {\it Fermi} LAT Bright Source List. These data provide identifications for 10 newly discovered $\gamma$-ray flat spectrum radio quasars (FSRQ)…
Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88,211 sources located at declination $\delta > -40^{\circ}$ and…
With their rapid, violent variability and broad featureless continuum emission, blazars have puzzled astronomers for over two decades. Today blazars represent the only extragalactic objects detected in high-energy gamma-rays. Their spectral…
Blazars are known to exhibit variability across a broad range of timescales. This behavior can include periodicity in their $\gamma$-ray emission, whose clear detection remains an ongoing challenge, partly due to the inherent stochasticity…
Since late 2007, we have been monitoring a large sample of known and likely gamma-ray-loud blazars at 15 GHz twice per week with the Owens Valley Radio Observatory (OVRO) 40 m Telescope. Our initial sample included the 1158 sources above…
We present results from the first two years of our fast-cadence 15 GHz gamma-ray blazar monitoring program, part of the F-GAMMA radio monitoring project. Our sample includes the 1158 blazars north of -20 degrees declination from the…
Aim: We have collected the most complete multi-wavelength ($6.0 - 6.0 \times 10^{-18} cm$) dataset of very high energy (VHE) $\gamma$-ray emitting (TeV) BL Lacs, which are the most numerous extragalactic VHE sources. Using significant…
This paper reports X-ray spectral observations of a relatively nearby z = 0.048 BL Lacertae (BL Lac) object 1ES1959+650, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect…
Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected…
Blazars have traditionally been separated into two broad categories based upon their optical emission characteristics; BL Lacs, with faint or no emission lines, and flat spectrum radio quasars (FSRQs) with prominent, broad emission lines.…
The VERITAS array of 12-m atmospheric-Cherenkov telescopes in southern Arizona is one of the world's most-sensitive detectors of very-high-energy (VHE, E>100 GeV) gamma rays. More than 50 extragalactic sources are known to emit VHE photons;…