Related papers: BL Lac candidates for TeV observations
We introduce a new method to determine the redshift of unknown-redshift BL Lac Objects. The method relies on simultaneous multi-wavelength (MWL) observations of BL Lac objects in optical, X-ray, HE (E>100 MeV) gamma-rays and VHE (E>100…
In this paper, we present results of TeV $\gamma$--ray observations of the high synchrotron peaked BL Lac object 1ES 1218+304 (z=0.182) with the $TACTIC$ (TeV Atmospheric Cherenkov Telescope with Imaging Camera). The observations are…
Nearly 50% of all sources detected by the Fermi Large Area Telescope are classified as blazars or blazar candidates, one of the most elusive classes of active galaxies. Additional blazars can also be hidden within the sample of unidentified…
We propose a method for setting upper limits to the extragalactic background light (EBL). Our method uses simultaneous {\em Fermi}-LAT and ground-based TeV observations of blazars and is based on the assumption that the intrinsic spectral…
A decade after the discovery of TeV gamma-rays from the blazar Mrk 421 (Punch et al. 1992), the list of TeV blazars has increased to five BL Lac objects: Mrk 421 (Punch et al. 1992; Petry et al. 1996; Piron et al. 2001), Mrk 501 (Quinn et…
Our goal is to research the upper limits on the extragalactic background light (EBL). The upper limits on the extragalactic background light (EBL), using the Fermi and very high energy (VHE) spectra recently observed in TeV blazars, are…
To date, only two extragalactic objects have been firmly established as very high-energy gamma-ray sources in the Northern sky: these are the two blazars Markarian 501 and Markarian 421. This paper reviews the most striking results obtained…
Published EGRET spectra from blazars extend only to 10 GeV, yet EGRET has detected approximately 2000 gamma-rays above 10 GeV of which about half are at high Galactic latitude. We report a search of these high-energy gamma-rays for…
In this work, we use two different methods to determine the opacity of the TeV gamma-rays caused by the extragalactic background light (EBL) via e-e+ production due to photon-photon interaction. The first method, Model-Dependent Approach,…
We report on our further analysis of the expanded and revised sample of potential BL Lac objects (the 2BL) optically identified from two catalogues of blue-selected (UV excess) point sources, the 2dF and 6dF QSO Redshift Surveys (2QZ and…
We report the results of an analysis to identify candidates for very high energy (VHE; E > 100 GeV) emission from high-latitude (|b|>10) unassociated sources in the year-1 catalog under development by the Fermi large area telescope (LAT)…
We report on ESO Very Large Telescope optical spectroscopy of 42 BL Lacertae objects of unknown redshift. Nuclear emission lines were observed in 12 objects, while for another six we detected absorption features due to their host galaxy.…
The fourth-DR3 version (4FGL-DR3) of the Fermi/LAT catalogue of $\gamma$-ray sources contains $\sim$ 1000 objects at a galactic latitude |b| > 10$^{\circ}$ which are not identified with an optical counterpart (UGS). We performed a…
We present and discuss polarimetric observations of 182 targets drawn from an optically selected sample of 240 probable BL Lac candidates out of the SDSS compiled by Collinge et al. (2005). In contrast to most other BL Lac candidate samples…
Variability is a prominent observational feature of blazars. The high-energy radiation mechanism of jets has always been important but still unclear. In this work, we performed a detailed analysis using Fermi-LAT data across 15 years and…
We have investigated TeV gamma-ray emissions from nearby X-ray selected BL Lac objects using the Utah Seven Telescope Array for more than two years. These objects can be considered as potential sources of TeV gamma rays with inverse compton…
Extremely high-peaked BL Lac objects - also named extreme blazars - are among the most energetic and persistent extragalactic accelerators in the Universe, defined by a synchrotron emission peaking above $10^{17}$ Hz in X-rays. Such…
Recent observations of blazars at high energy (HE, 0.1-100 GeV) and very high energy (VHE, >0.1 TeV) have provided important constraints on the intensity and spectrum of the diffuse Extragalactic Background Light (EBL), shedding light on…
Photons with very high energy up to TeV (VHE) emitted from active galactic nuclei (AGNs) provide some invaluable information of the origin of $\gam$-ray emission. Although 66 blazars have been detected by {\it EGRET}, only three low…
Very-high energy (VHE; $>$100 GeV) $\gamma$-ray emission originates via some of the most extreme particle acceleration processes in the universe. Considering beamed active galactic nuclei, i.e., blazars, only a small fraction, mainly high…