Related papers: Whipple Observations of BL Lac Objects

Absorption features in sub-TeV gamma-ray spectra of BL Lac objects

The production site of gamma rays in blazars is closely related to their interaction with the photon fields surrounding the active galactic nucleus. In this paper, we discuss an indirect method that may help to unveil the presence of…

High Energy Astrophysical Phenomena · Physics 2022-02-21 L. Foffano , V. Vittorini , M. Tavani , E. Menegoni

Egret (GeV) Blazars

The EGRET instrument on the Compton Gamma Ray Observatory (1991-2000) has positively detected high energy gamma-ray emission from more than 67 active galaxies of the blazar class. The majority of the EGRET blazars are flat-spectrum radio…

Astrophysics · Physics 2009-11-06 R. Mukherjee

Detection of VHE radiation from the BL Lac PG 1553+113 with the MAGIC telescope

In 2005 and 2006, the MAGIC telescope has observed very high energy gamma-ray emission from the distant BL Lac object PG 1553+113. The overall significance of the signal is 8.8 sigma for 18.8h observation time. The light curve shows no…

Astrophysics · Physics 2009-11-11 J. Albert et al.

Very high energy observations of the BL Lac objects 3C 66A and OJ 287

Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we have observed the BL Lac objects 3C 66A and OJ 287. These are members of the class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three LBLs…

Astrophysics · Physics 2008-11-26 T. Lindner , D. S. Hanna , J. Kildea , J. Ball , D. A. Bramel , J. Carson , C. E. Covault , D. Driscoll , P. Fortin , D. M. Gingrich , A. Jarvis , C. Mueller , R. Mukherjee , R. A. Ong , K. Ragan , R. A. Scalzo , D. A. Williams , J. Zweerink

Optical spectroscopic observations of gamma-ray blazars candidates I: preliminary results

A significant fraction ($\sim 30$ %) of the gamma-ray sources listed in the second $\textit{Fermi}$ LAT (2FGL) catalog is still of unknown origin, being not yet associated with counterparts at lower energies. Using the available information…

High Energy Astrophysical Phenomena · Physics 2015-06-19 A. Paggi , D. Milisavljevic , N. Masetti , E. Jiménez-Bailón , V. Chavushyan , R. D'Abrusco , F. Massaro , M. Giroletti , H. A. Smith , R. Margutti , G. Tosti , J. R. Martínez-Galarza , H. Otí-Floranes , M. Landoni , J. E. Grindlay , S. Funk

Very High Energy Gamma-Ray Emission from the Blazar Markarian 421

Very high energy gamma-ray emission from the BL Lac object Markarian 421 has been detected over three observing seasons on 59 nights between April 1992 and June 1994 with the Whipple 10-meter imaging Cherenkov telescope. During its initial…

Astrophysics · Physics 2009-10-28 M. S. Schubnell , C. W. Akerlof , S. Biller J. Buckley , D. A. Carter-Lewis , M. F. Cawley , M. Chantell , V. Connaughton , D. J. Fegan , S. Fennell , J. A. Gaidos , A. M. Hillas , A. D. Kerrick R. C. Lamb , D. I. Meyer , G. Mohanty , J. Rose , A. C. Rovero , G. Sembroski , T. C. Weekes , C. Wilson , J. Zweerink

Blazar Discoveries with VERITAS

Blazars are among the most energetic and violent objects in the universe. By observing blazars at very high energies (VHE, E > 100 GeV) we can better understand blazar emission mechanisms, jet structure, black hole accretion and the…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-13 J. S. Perkins

Discovery of VHE gamma-rays from the BL Lac object PKS 0548-322

PKS 0548-322 (z=0.069) is a ``high-frequency-peaked'' BL Lac object and a candidate very high energy (VHE, E>100 GeV) gamma-ray emitter, due to its high X-ray and radio flux. Observations at the VHE band provide insights into the origin of…

High Energy Astrophysical Phenomena · Physics 2015-05-19 H. E. S. S. collaboration , : , F. Aharonian , A. G. Akhperjanian , G. Anton , U. Barres de Almeida , A. R. Bazer-Bachi , Y. Becherini , B. Behera , W. Benbow , K. Bernlöhr , A. Bochow , C. Boisson , J. Bolmont , V. Borrel , J. Brucker , F. Brun , P. Brun , R. Bühler , T. Bulik , I. Büsching , T. Boutelier , P. M. Chadwick , A. Charbonnier , R. C. G. Chaves , A. Cheesebrough , L. -M. Chounet , A. C. Clapson , G. Coignet , M. Dalton , M. K. Daniel , I. D. Davids , B. Degrange , C. Deil , H. J. Dickinson , A. Djannati-Ataï , W. Domainko , L. O'C. Drury , F. Dubois , G. Dubus , J. Dyks , M. Dyrda , K. Egberts , D. Emmanoulopoulos , P. Espigat , C. Farnier , F. Feinstein , A. Fiasson , A. Förster , G. Fontaine , M. Füssling , S. Gabici , Y. A. Gallant , L. Gérard , D. Gerbig , B. Giebels , J. F. Glicenstein , B. Glück , P. Goret , D. Göring , D. Hauser , M. Hauser , S. Heinz , G. Heinzelmann , G. Henri , G. Hermann , J. A. Hinton , A. Hoffmann , W. Hofmann , M. Holleran , S. Hoppe , D. Horns , A. Jacholkowska , O. C. de Jager , C. Jahn , I. Jung , K. Katarzyński , U. Katz , S. Kaufmann , E. Kendziorra , M. Kerschhagg , D. Khangulyan , B. Khélifi , D. Keogh , W. Kluźniak , T. Kneiske , Nu. Komin , K. Kosack , G. Lamanna , J. -P. Lenain , T. Lohse , V. Marandon , J. M. Martin , O. Martineau-Huynh , A. Marcowith , J. Masbou , D. Maurin , T. J. L. McComb , M. C. Medina , R. Moderski , E. Moulin , M. Naumann-Godo , M. de Naurois , D. Nedbal , D. Nekrassov , B. Nicholas , J. Niemiec , S. J. Nolan , S. Ohm , J-F. Olive , E. de Oña Wilhelm , K. J. Orford , M. Ostrowski , M. Panter , M. Paz Arribas , G. Pedaletti , G. Pelletier , P. -O. Petrucci , S. Pita , G. Pühlhofer , M. Punch , A. Quirrenbach , B. C. Raubenheimer , M. Raue , S. M. Rayner , M. Renaud , F. Rieger , J. Ripken , L. Rob , S. Rosier-Lees , G. Rowell , B. Rudak , C. B. Rulten , J. Ruppel , V. Sahakian , A. Santangelo , R. Schlickeiser , F. M. Schöck , R. Schröder , U. Schwanke , S. Schwarzburg , S. Schwemmer , A. Shalchi , M. Sikora , J. L. Skilton , H. Sol , D. Spangler , L. Stawarz , R. Steenkamp , C. Stegmann , F. Stinzing , G. Superina , A. Szostek , P. H. Tam , J. -P. Tavernet , R. Terrier , O. Tibolla , M. Tluczykont , C. van Eldik , G. Vasileiadis , C. Venter , L. Venter , J. P. Vialle , P. Vincent , M. Vivier , H. J. Völk , F. Volp , S. J. Wagner , M. Ward , A. A. Zdziarski , A. Zech

Detection of Very-High Energy Gamma-Rays from the BL Lac Object PG 1553+113 with the MAGIC Telescope

The MAGIC telescope has observed very-high energy gamma-ray emission from the BL Lac object PG 1553+113 in 2005 and 2006 at an overall significance is 8.8 sigma. The light curve shows no significant flux variations on a daily timescale. The…

Astrophysics · Physics 2019-08-15 Robert Wagner , Daniela Dorner , Masaaki Hayashida , Thomas Hengstebeck , Daniel Kranich , Daniel Mazin , Diego Tescaro , Nina Nowak

The First VHE Activity of OJ 287 and the Extragalactic Background Light

The BL Lacertae (BL Lac) object OJ 287 underwent an intense X-ray activity phase, exhibiting its brightest recorded X-ray flare in 2016-2017, characterized by much softer X-ray spectra and, concurrently, its first-ever recorded…

High Energy Astrophysical Phenomena · Physics 2024-07-10 Sameer Yadav , Pankaj Kushwaha

High Galactic latitude Fermi sources of gamma-rays with energies above 100 GeV

We present a catalog of sources of very high energy (E>100 GeV) gamma-rays detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope at Galactic latitudes |b|>=10 degrees. We cross-correlate the directions of…

High Energy Astrophysical Phenomena · Physics 2015-05-18 A. Neronov , D. V. Semikoz , Ie. Vovk

NuSTAR Observations and multi-wavelength modeling of the high-redshift BL Lac Object 4FGL J2146.5-1344

High synchrotron peak (HSP; $\nu_{sy}^{pk} > 10^{15}$ Hz) BL Lacs are some of the most extreme accelerators in the Universe. Those found at high redshifts ($z>1$) challenge our understanding of blazar evolution models and are crucial for…

High Energy Astrophysical Phenomena · Physics 2020-02-12 M. Rajagopal , L. Marcotulli , M. Ajello , A. Kaur , V. Paliya , D. Hartmann

Discovery of Very High Energy gamma-rays from the blazar S5 0716+714

The MAGIC collaboration reports the detection of the blazar S50716+714 (redshift uncertain) in very high energy gamma-rays. The observations were performed in November 2007 and in April 2008, and were triggered by the KVA telescope due to…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-13 D. Mazin , E. Lindfors , K. Berger , N. Galante , E. Prandini , T. Saito

TeV gamma-ray observations from nearby AGNs by Utah Seven Telescope Array

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…

Astrophysics · Physics 2012-08-27 The Utah Seven Telescope Array collaboration

Testing the ubiquitous presence of very high energy emission in gamma-ray bursts with the MAGIC telescopes

Gamma-ray bursts (GRBs) are the most powerful transient objects in the Universe, and they are a primary target for the MAGIC Collaboration. Recognizing the challenges of observing these elusive objects with Imaging Atmospheric Cherenkov…

High Energy Astrophysical Phenomena · Physics 2025-12-24 S. Abe , J. Abhir , A. Abhishek , V. A. Acciari , A. Aguasca-Cabot , I. Agudo , T. Aniello , S. Ansoldi , L. A. Antonelli , A. Arbet Engels , C. Arcaro , T. T. H. Arnesen , K. Asano , A. Babic , C. Bakshi , U. Barres de Almeida , J. A. Barrio , L. Barrios-Jimenez , I. Batkovic , J. Baxter , J. Becerra Gonzalez , W. Bednarek , E. Bernardini , J. Bernete , A. Berti , J. Besenrieder , C. Bigongiari , A. Biland , O. Blanch , G. Bonnoli , Ž. Bošnjak , E. Bronzini , I. Burelli , A. Campoy-Ordaz , A. Carosi , R. Carosi , M. Carretero-Castrillo , A. J. Castro-Tirado , D. Cerasole , G. Ceribella , Y. Chai , A. Cifuentes , J. L. Contreras , J. Cortina , S. Covino , G. D'Amico , P. Da Vela , F. Dazzi , A. De Angelis , B. De Lotto , R. de Menezes , M. Delfino , J. Delgado , C. Delgado Mendez , F. Di Pierro , R. Di Tria , L. Di Venere , A. Dinesh , D. Dominis Prester , A. Donini , D. Dorner , M. Doro , L. Eisenberger , D. Elsaesser , J. Escudero , L. Fariña , A. Fattorini , L. Foffano , L. Font , S. Fröse , S. Fukami , Y. Fukazawa , R. J. García López , S. García Soto , M. Garczarczyk , S. Gasparyan , M. Gaug , J. G. Giesbrecht Paiva , N. Giglietto , F. Giordano , P. Gliwny , N. Godinovic , T. Gradetzke , R. Grau , D. Green , J. G. Green , P. Günther , D. Hadasch , A. Hahn , T. Hassan , L. Heckmann , J. Herrera Llorente , D. Hrupec , R. Imazawa , S. Inoue , D. Israyelyan , J. Jahanvi , I. Jiménez Martínez , J. Jiménez Quiles , J. Jormanainen , S. Kankkunen , T. Kayanoki , J. Konrad , P. M. Kouch , H. Kubo , J. Kushida , M. Láinez , A. Lamastra , E. Lindfors , S. Lombardi , F. Longo , R. López-Coto , M. López-Moya , A. López-Oramas , S. Loporchio , L. Lulic , E. Lyard , P. Majumdar , M. Makariev , M. Mallamaci , G. Maneva , M. Manganaro , S. Mangano , K. Mannheim , S. Marchesi , M. Mariotti , M. Martínez , P. Maruševec , A. Mas-Aguilar , D. Mazin , S. Menchiari , J. Méndez Gallego , S. Menon , D. Miceli , J. M. Miranda , R. Mirzoyan , M. Molero González , E. Molina , H. A. Mondal , A. Moralejo , E. Moretti , T. Nakamori , C. Nanci , L. Nava , V. Neustroev , L. Nickel , M. Nievas Rosillo , C. Nigro , L. Nikolic , K. Nilsson , K. Nishijima , K. Noda , S. Nozaki , A. Okumura , J. Otero-Santos , S. Paiano , D. Paneque , R. Paoletti , J. M. Paredes , M. Peresano , M. Persic , M. Pihet , G. Pirola , F. Podobnik , P. G. Prada Moroni , E. Prandini , M. Ribó , J. Rico , C. Righi , N. Sahakyan , T. Saito , F. G. Saturni , K. Schmitz , F. Schmuckermaier , A. Sciaccaluga , G. Silvestri , A. Simongini , J. Sitarek , V. Sliusar , D. Sobczynska , A. Stamerra , J. Striškovic , D. Strom , M. Strzys , Y. Suda , H. Tajima , M. Takahashi , R. Takeishi , P. Temnikov , K. Terauchi , T. Terzic , M. Teshima , A. Tutone , S. Ubach , J. van Scherpenberg , M. Vazquez Acosta , S. Ventura , G. Verna , I. Viale , A. Vigliano , C. F. Vigorito , E. Visentin , V. Vitale , I. Vovk , R. Walter , F. Wersig , M. Will , T. Yamamoto , P. K. H. Yeung

Discovery of High-energy and Very High Energy Gamma-ray Emission from the Blazar RBS 0413

We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high-energy (VHE; E > 100 GeV) gamma-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based gamma-ray observatory, detected VHE gamma…

High Energy Astrophysical Phenomena · Physics 2015-06-04 VERITAS Collaboration , E. Aliu , S. Archambault , T. Arlen , T. Aune , M. Beilicke , W. Benbow , M. Boettcher , A. Bouvier , S. M. Bradbury , J. H. Buckley , V. Bugaev , K. Byrum , A. Cannon , A. Cesarini , L. Ciupik , E. Collins-Hughes , M. P. Connolly , P. Coppi , W. Cui , G. Decerprit , R. Dickherber , J. Dumm , M. Errando , A. Falcone , Q. Feng , J. P. Finley , G. Finnegan , L. Fortson , A. Furniss , N. Galante , D. Gall , S. Godambe , S. Griffin , J. Grube , G. Gyuk , D. Hanna , K. Hawkins , J. Holder , H. Huan , G. Hughes , T. B. Humensky , P. Kaaret , N. Karlsson , M. Kertzman , Y. Khassen , D. Kieda , H. Krawczynski , F. Krennrich , M. J. Lang , K. Lee , A. S Madhavan , G. Maier , P. Majumdar , S. McArthur , A. McCann , P. Moriarty , R. Mukherjee , R. A. Ong , M. Orr , A. N. Otte , N. Palma , N. Park , J. S. Perkins , A. Pichel , M. Pohl , H. Prokoph , J. Quinn , K. Ragan , L. C. Reyes , P. T. Reynolds , E. Roache , H. J. Rose , J. Ruppel , D. B. Saxon , M. Schroedter , G. H. Sembroski , G. D. Senturk , A. W. Smith , D. Staszak , I. Telezhinsky , G. Tesic , M. Theiling , S. Thibadeau , K. Tsurusaki , A. Varlotta , M. Vivier , S. P. Wakely , J. E. Ward , T. C. Weekes , A. Weinstein , T. Weisgarber , D. A. Williams , B. Zitzer , P. Fortin , D. Horan

Extreme synchrotron blazars: the case of Mkn 501

BeppoSAX observations of Mkn501 in April 1997 (Pian et al. 1998), have revealed an extraordinary X-ray emission from this BL Lac object, during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA and CAT Cerenkov…

Astrophysics · Physics 2015-06-24 G. Ghisellini

Observations of the Crab Nebula, Mkn 501 and Mkn 421 using the TACTIC Imaging Element

The results of our observational campaigns on the two extragalactic sources Mkn 501 and Mkn 421, carried out with the Imaging Element of the TACTIC array, during March-May, 1998 and April-May, 1999, are presented. The results indicate that…

Astrophysics · Physics 2007-05-23 N. Bhatt , N. K. Agarwal , C. K. Bhat , S. Bhattacharyya , V. K. Dhar , A. Goyal , H. C. Goyal , C. L. Kaul , D. K. Koul , I. K. Kaul , R. K. Kaul , S. K. Kaul , S. R. Kaul , M. K. Koul , R. Koul , M. Kothari , R. C. Rannot , A. K. Razdan , S. Sahayanathan , M. L. Sapru , N. Satyabhama , A. K. Tickoo , N. Venugopal , K. K. Yadav , C. L. Bhat

Measuring the extragalactic background light from very high energy gamma-ray observations of blazars

The extragalactic background light (EBL) contains important information about stellar and galaxy evolution. It leaves imprint on the very high energy $\gamma$-ray spectra from sources at cosmological distances due to the process of pair…

High Energy Astrophysical Phenomena · Physics 2012-12-27 Qiang Yuan , Hai-Liang Huang , Xiao-Jun Bi , Hong-Hao Zhang

Very-high-energy gamma-ray emission from high-redshift blazars

We study the possible detection of and properties of very high-energy (VHE) gamma-ray emission (in the energy band above 100 GeV) from high redshift sources. We report on the detection of VHE gamma-ray flux from blazars with redshifts…

High Energy Astrophysical Phenomena · Physics 2015-08-20 A. Neronov , D. V. Semikoz , A. M. Taylor , Ie. Vovk