Related papers: Whipple Observations of BL Lac Objects
Two active galactic nuclei have been detected at TeV energies using the atmospheric Cherenkov imaging technique. The Whipple Observatory gamma-ray telescope has been used to observe all the BL Lacertae objects in the northern hemisphere out…
All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far at very high energy (VHE) gamma-rays belong to the class of high-frequency peaked BL Lac (HBL) objects. This suggested to us a systematic scan of candidate sources…
Extremely High energy peaked BL Lac (EHBL) objects are a special class of blazars with peculiar observational properties at X-ray and $\gamma$--ray energies. The observations of these sources indicate hard X-ray and $\gamma$--ray spectra…
We present the discovery of >350 GeV gamma-ray emission from the BL Lacertae object 1ES 2344+514 with the Whipple Observatory 10m gamma-ray telescope. This is the third BL Lac object detected at gamma-ray energies above 300 Gev, the other…
Extreme high-energy peaked BL Lac objects (EHBLs) are blazars whose synchrotron emission peaks at exceptionally high energies, above few keV, in the hard X-ray regime. So far, only a handful of those objects has been detected at very high…
Context. The study of BL Lac objects (BLL) detected in gamma-rays gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool to constrain the density of the extragalactic background light. As their…
High-energy observations of extreme BL Lac objects, such as 1ES0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic…
High energy observations of extreme BL Lac objects, such as 1ES 0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic…
Our understanding of blazars has been greatly increased in recent years by extensive multi-wavelength observations, particularly in the radio, X-ray and gamma-ray regions. Over the past decade the Whipple 10m telescope has contributed to…
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…
We present the first strong detection of very high energy gamma-rays from the close (z=0.048) X-ray selected BL Lacertae object 1ES1959+650. Observations were made with the Whipple 10m telescope on Mt. Hopkins, Arizona, using the…
Approximately 25 blazars are know to emit VHE (E>100 GeV) gamma rays. Understanding these powerful objects requires long-term, intense, monitoring observations since they exhibit strong, rapid and irregular variability across the entire…
We present results from observations of 29 BL Lacertae objects, taken with the Whipple Observatory 10 m Gamma-Ray Telescope between 1995 and 2000. The observed objects are mostly at low redshift (z < 0.2) but observations of objects of z up…
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…
Aims. We aim to determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects. Methods. We secured medium resolution optical and near-infrared spectra of 4 bright BL Lac objects of unknown redshift using the…
The active galactic nucleus BL Lac was observed with the Gt-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23-September 1, 1998, in order to search for ultrahigh-energy gamma-ray (>1 TeV) emission. The…
We present multi-wavelength observations of the very high energy (VHE, E >250 GeV) gamma-ray sources Mrk 421 and Mrk 501. The VHE data presented here were taken with the Whipple Observatory 10m gamma-ray telescope. In the Mrk 421 campaign,…
We present multiwavelength observations of the BL Lacertae object Markarian 501 (Mrk 501) in 1997 between April 8 and April 19. Evidence of correlated variability is seen in very high energy (VHE, E > 350 GeV) gamma-ray observations taken…
We found significant correlations between the arrival directions of the highest energy photons (E>10 GeV) observed by EGRET and positions of the BL Lac type objects (BL Lacs). The observed correlations imply that not less than three per…
BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1--10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission…