Related papers: TeV and Multi-wavelength Observations of Mrk 421 i…

Observations of TeV gamma-rays from Mrk 421 during Dec. 2005 to Apr. 2006 with the TACTIC telescope

The TACTIC $\gamma$-ray telescope has observed Mrk 421 on 66 clear nights from Dec. 07, 2005 to Apr. 30, 2006, totalling $\sim$ 202 hours of on-source observations. Here, we report the detection of flaring activity from the source at $\geq$…

Astrophysics · Physics 2008-11-26 K. K. Yadav , P. Chandra , A. K. Tickoo , R. C. Rannot , S. Godambe , M. K. Koul , V. K. Dhar , S. Thoudam , N. Bhatt , S. Bhattacharyya , K. Chanchalani , H. C. Goyal , R. K. Kaul , M. Kothari , S. Kotwal , R. Koul , S. Sahayanathan , M. Sharma , K. Venugopal

Observation of Markarian 421 in TeV gamma rays over a 14-year time span

The variability of the blazar Markarian 421 in TeV gamma rays over a 14-year time period has been explored with the Whipple 10 m telescope. It is shown that the dynamic range of its flux variations is large and similar to that in X-rays. A…

High Energy Astrophysical Phenomena · Physics 2015-06-17 V. A. Acciari , T. Arlen , T. Aune , W. Benbow , R. Bird , A. Bouvier , S. M. Bradbury , J. H. Buckley , V. Bugaev , I. de la Calle Perez , D. A. Carter-Lewis , A. Cesarini , L. Ciupik , E. Collins-Hughes , M. P. Connolly , W. Cui , C. Duke , J. Dumm , A. Falcone , S. Federici , D. J. Fegan , S. J. Fegan , J. P. Finley , G. Finnegan , L. Fortson , J. Gaidos , N. Galante , D. Gall , K. Gibbs , G. H. Gillanders , S. Griffin , J. Grube , G. Gyuk , D. Hanna , D. Horan , T. B. Humensky , P. Kaaret , M. Kertzman , Y. Khassen , D. Kieda , H. Krawczynski , F. Krennrich , M. J. Lang , J. E. McEnery , A. S. Madhavan , P. Moriarty , T. Nelson , A. O'Faoláin de Bhróithe , R. A. Ong , M. Orr , A. N. Otte , J. S. Perkins , D. Petry , A. Pichel , M. Pohl , J. Quinn , K. Ragan , P. T. Reynolds , E. Roache , A. Rovero , M. Schroedter , G. H. Sembroski , A. Smith , I. Telezhinsky , M. Theiling , J. Toner , J. Tyler , A. Varlotta , M. Vivier , S. P. Wakely , J. E. Ward , T. C. Weekes , A. Weinstein , R. Welsing , D. A. Williams , S. Wissel

Discovery of Spectral Variability of Markarian 421 at TeV Energies

The detection of spectral variability of the gamma-ray blazar Mrk 421 at TeV energies is reported. Observations with the Whipple Observatory 10m gamma-ray telescope taken in 2000/2001 revealed exceptionally strong and long-lasting flaring…

Astrophysics · Physics 2009-11-07 F. Krennrich , I. H. Bond , S. M. Bradbury , J. H. Buckley , D. A. Carter-Lewis , W. Cui , I. de la Calle Perez , D. J. Fegan , S. J. Fegan , J. P. Finley , J. A. Gaidos , K. Gibbs , G. H. Gillanders , T. A. Hall , A. M. Hillas , J. Holder , D. Horan , M. Jordan , M. Kertzman , D. Kieda , J. Kildea , J. Knapp , K. Kosack , M. J. Lang , S. LeBohec , P. Moriarty , D. Müller , R. A. Ong , R. Pallassini , D. Petry , J. Quinn , N. W. Reay , P. T. Reynolds , H. J. Rose , G. H. Sembroski , R. Sidwell , N. Stanton , S. P. Swordy , V. V. Vassiliev , S. P. Wakely , T. C. Weekes

A search for spectral hysteresis and energy-dependent time lags from X-ray and TeV gamma-ray observations of Mrk 421

Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray…

High Energy Astrophysical Phenomena · Physics 2016-12-28 A. U. Abeysekara , S. Archambault , A. Archer , W. Benbow , R. Bird , M. Buchovecky , J. H. Buckley , V. Bugaev , J. V Cardenzana , M. Cerruti , X. Chen , L. Ciupik , M. P. Connolly , W. Cui , J. D. Eisch , A. Falcone , Q. Feng , J. P. Finley , H. Fleischhack , A. Flinders , L. Fortson , A. Furniss , S. Griffin , M. Hütten , N. Håkansson , D. Hanna , O. Hervet , J. Holder , T. B. Humensky , P. Kaaret , P. Kar , M. Kertzman , D. Kieda , M. Krause , S. Kumar , M. J. Lang , G. Maier , S. McArthur , A. McCann , K. Meagher , P. Moriarty , R. Mukherjee , D. Nieto , S. O'Brien , R. A. Ong , A. N. Otte , N. Park , V. Pelassa , M. Pohl , A. Popkow , E. Pueschel , K. Ragan , P. T. Reynolds , G. T. Richards , E. Roache , I. Sadeh , M. Santander , G. H. Sembroski , K. Shahinyan , D. Staszak , I. Telezhinsky , J. V. Tucci , J. Tyler , S. P. Wakely , A. Weinstein , A. Wilhelm , D. A. Williams , M. L. Ahnen , S. Ansoldi , L. A. Antonelli , P. Antoranz , C. Arcaro , A. Babic , B. Banerjee , P. Bangale , U. Barres de Almeida , J. A. Barrio , J. Becerra González , W. Bednarek , E. Bernardini , A. Berti , B. Biasuzzi , A. Biland , O. Blanch , S. Bonnefoy , G. Bonnoli , F. Borracci , T. Bretz , R. Carosi , A. Carosi , A. Chatterjee , P. Colin , E. Colombo , J. L. Contreras , J. Cortina , S. Covino , P. Cumani , P. Da Vela , F. Dazzi , A. De Angelis , B. De Lotto , E. de Oña Wilhelmi , F. Di Pierro , M. Doert , A. Domínguez , D. Dominis Prester , D. Dorner , M. Doro , S. Einecke , D. Eisenacher Glawion , D. Elsaesser , M. Engelkemeier , V. Fallah Ramazani , A. Fernández-Barral , D. Fidalgo , M. V. Fonseca , L. Font , C. Fruck , D. Galindo , R. J. García López , M. Garczarczyk , M. Gaug , P. Giammaria , N. Godinović , D. Gora , D. Guberman , D. Hadasch , A. Hahn , T. Hassan , M. Hayashida , J. Herrera , J. Hose , D. Hrupec , G. Hughes , W. Idec , K. Kodani , Y. Konno , H. Kubo , J. Kushida , D. Lelas , E. Lindfors , S. Lombardi , F. Longo , M. López , R. López-Coto , P. Majumdar , M. Makariev , K. Mallot , G. Maneva , M. Manganaro , K. Mannheim , L. Maraschi , B. Marcote , M. Mariotti , M. Martínez , D. Mazin , U. Menzel , R. Mirzoyan , A. Moralejo , E. Moretti , D. Nakajima , V. Neustroev , A. Niedzwiecki , M. Nievas Rosillo , K. Nilsson , K. Nishijima , K. Noda , L. Nogués , M. Nöthe , S. Paiano , J. Palacio , M. Palatiello , D. Paneque , R. Paoletti , J. M. Paredes , X. Paredes-Fortuny , G. Pedaletti , M. Peresano , L. Perri , M. Persic , J. Poutanen , P. G. Prada Moroni , E. Prandini , I. Puljak , J. R. Garcia , I. Reichardt , W. Rhode , M. Ribó , J. Rico , T. Saito , K. Satalecka , S. Schroeder , T. Schweizer , S. N. Shore , A. Sillanpää , J. Sitarek , I. Snidaric , D. Sobczynska , A. Stamerra , M. Strzys , T. Surić , L. Takalo , F. Tavecchio , P. Temnikov , T. Terzić , D. Tescaro , M. Teshima , D. F. Torres , N. Torres-Albà , T. Toyama , A. Treves , G. Vanzo , M. Vazquez Acosta , I. Vovk , J. E. Ward , M. Will , M. H. Wu , R. Zanin , T. Hovatta , I. de la Calle Perez , P. S. Smith , E. Racero , M. Baloković

Discovery of a new TeV gamma-ray source: VER J0521+211

We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov telescope array. These observations were motivated by the discovery of a cluster of >30GeV…

High Energy Astrophysical Phenomena · Physics 2013-10-04 VERITAS Collaboration , S. Archambault , T. Arlen , T. Aune , M. Beilicke , W. Benbow , R. Bird , A. Bouvier , J. H. Buckley , V. Bugaev , K. Byrum , A. Cesarini , L. Ciupik , M. P. Connolly , W. Cui , M. Errando , A. Falcone , S. Federici , Q. Feng , J. P. Finley , L. Fortson , A. Furniss , N. Galante , D. Gall , G. H. Gillanders , S. Griffin , J. Grube , G. Gyuk , D. Hanna , J. Holder , G. Hughes , T. B. Humensky , P. Kaaret , M. Kertzman , Y. Khassen , D. Kieda , H. Krawczynski , F. Krennrich , S. Kumar , M. J. Lang , A. S Madhavan , G. Maier , P. Majumdar , S. McArthur , A. McCann , J. Millis , P. Moriarty , R. Mukherjee , A. O'Faolain de Bhroithe , R. A. Ong , A. N. Otte , N. Park , J. S. Perkins , M. Pohl , A. Popkow , H. Prokoph , J. Quinn , K. Ragan , L. C. Reyes , P. T. Reynolds , G. T. Richards , E. Roache , D. B. Saxon , G. H. Sembroski , A. W. Smith , D. Staszak , I. Telezhinsky , M. Theiling , A. Varlotta , V. V. Vassiliev , S. Vincent , S. P. Wakely , T. C. Weekes , A. Weinstein , R. Welsing , D. A. Williams , B. Zitzer , M. Bottcher , S. J. Fegan , P. Fortin , J. P. Halpern , Y. Y. Kovalev , M. L. Lister , J. Liu , A. B. Pushkarev , P. S. Smith

Multiwavelength study of TeV Blazar Mrk421 during giant flare

Context: The nearby (z=0.031) TeV blazar Mrk421 was reported to be in a high state of flux activity since November, 2009. Aims: To investigate possible changes in the physical parameters of Mrk421 during its high state of activity using…

High Energy Astrophysical Phenomena · Physics 2015-06-04 A. Shukla , V. R. Chitnis , P. R. Vishwanath , B. S. Acharya , G. C. Anupama , P. Bhattacharjee , R. J. Britto , T. P. Prabhu , L. Saha , B. B. Singh

News from a Multi-Wavelength Monitoring Campaign on Mrk 421

We conducted a daily monitoring campaign on Mrk 421 in 2003 and 2004 with the Whipple 10 m telescope and the large-area instruments aboard RXTE, simultaneously covering TeV and X-ray energies. Supporting observations at optical and radio…

Astrophysics · Physics 2019-08-14 Wei Cui

Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability

(Abridged) We present a detailed analysis of week-long simultaneous observations of the blazar Mrk421 at 2-60 keV X-rays (RXTE) and TeV gamma-rays (Whipple and HEGRA) in 2001. The unprecedented quality of this dataset enables us to…

Astrophysics · Physics 2008-06-16 G. Fossati , J. H. Buckley , I. H. Bond , S. M. Bradbury , D. A. Carter-Lewis , Y. C. K. Chow , W. Cui , A. D. Falcone , J. P. Finley , J. A. Gaidos , J. Grube , J. Holder , D. Horan , D. Horns , M. M. Jordan , D. B. Kieda , J. Kildea , H. Krawczynski , F. Krennrich , M. J. Lang , S. LeBohec , K. Lee , P. Moriarty , R. A. Ong , D. Petry , J. Quinn , G. H. Sembroski , S. P. Wakely , T. C. Weekes

Highlights of Recent Multiwavelength Observations of VHE Blazars with VERITAS

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…

High Energy Astrophysical Phenomena · Physics 2019-08-13 J. Grube

The relentless variability of Mrk 421 from the TeV to the radio

The origin of the gamma-ray emission of the blazar Mrk 421 is still a matter of debate. We used 5.5 years of unbiased observing campaign data, obtained using the FACT telescope and the Fermi LAT detector at TeV and GeV energies, the longest…

High Energy Astrophysical Phenomena · Physics 2021-03-17 Axel Arbet-Engels , Dominik Baack , Matteo Balbo , Adrian Biland , Michael Blank , Thomas Bretz , Kai Bruegge , Michael Bulinski , Jens Buss , Manuel Doerr , Daniela Dorner , Dominik Elsaesser , Dorothee Hildebrand , Karl Mannheim , Sebastian Mueller , Dominik Neise , Maximilian Noethe , Aleksander Paravac , Wolfgang Rhode , Bernd Schleicher , Kevin Sedlaczek , Amit Shukla , Vitalii Sliusar , Roland Walter , Elan von Willert

Study of short term enhanced TeV $\gamma$- ray emission from Mrk 421 observed with TACTIC on December 28, 2014

In this work, we report on the detection of enhanced TeV gamma- ray emission from the high synchrotron-peaked blazar Mrk 421 with the TACTIC telescope on the night of December 28, 2014 (MJD 57019). We use data from the TACTIC observations…

High Energy Astrophysical Phenomena · Physics 2018-08-29 K K Singh , K K Yadav , K Chanchalani , P Chandra , B Ghosal , A K Tickoo , R C Rannot , P Marandi , N K Agarwal , M Kothari , K K Gour , H C Goyal , A Goyal , N Kumar , C Borwankar , S R Kaul , V K Dhar , M K Koul , R Koul , K Venugopal , C K Bhat , N Chouhan

Multiwavelength Observations of the Blazar Mrk 421 in December 2002 and January 2003

We report on a multiwavelength campaign on the TeV gamma-ray blazar Markarian (Mrk) 421 performed during December 2002 and January 2003. These target of opportunity observations were initiated by the detection of X-ray and TeV gamma-ray…

Astrophysics · Physics 2019-08-15 P. Rebillot , M. Aller , H. Aller , P. Boltwood , I. Jung , D. Kranich , A. Sillanpaa , A. Sadun

Hourly Spectral Variability of Mrk 421

Mrk 421 is the first TeV blazar found to exhibit significant spectral variability during strong flaring activity, showing hardening of the TeV spectrum in high emission states. Mrk 421 is also known to exhibit flux variability on time…

Astrophysics · Physics 2009-09-29 F. Krennrich , I. H. Bond , P. J. Boyle , S. M. Bradbury , J. H. Buckley

Multiwavelength Observations of the Blazar VER J0521+211 During an Elevated TeV Gamma-Ray State

We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211 observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral flux above 200 GeV measured with the nightly-binned light curve is $(8.8 \pm 0.4)…

High Energy Astrophysical Phenomena · Physics 2022-08-10 The VERITAS Collaboration , The MAGIC Collaboration

TeV Gamma-Ray Observations of Mrk421 and H1426+428 with TACTIC Imaging Telescope

We have observed extragalactic sources Mrk421 (z=0.30) and H1426+428 (z=0.129) in very high energy gamma region using TACTIC telescope at Mount Abu, Rajasthan, India. Mrk421 was observed during 07 December 2005 to 18 April 2007 for a total…

Cosmology and Nongalactic Astrophysics · Physics 2011-09-12 Kuldeep Yadav

Variations of the TeV energy spectrum at different flux levels of Mkn 421 observed with the HEGRA system of Cherenkov telescopes

The nearby BL Lacertae (BL Lac) object Markarian~421 (Mkn~421) at a red shift z=0.031 was observed to undergo strong TeV Gamma-ray outbursts in the observational periods from December 1999 until May 2001. The time averaged energy spectrum…

Astrophysics · Physics 2008-11-26 HEGRA Collaboration , F. Aharonian

The TeV Energy Spectrum of Mrk 421 Measured in A High Flaring State

The BL Lac object (blazar) Mrk 421 was observed during its outburst in April 2004 with the Whipple 10 m telescope for a total of about 24.5 hours. The measured gamma-ray rate varied substantially over the range from 4 to 10 gamma's/min and…

Astrophysics · Physics 2009-11-13 A. Konopelko , W. Cui , C. Duke , J. P. Finley

Multi-wavelength Observations of LS I +61 303 with VERITAS, Swift and RXT E: 2006-2008

A long term, multi-wavelength monitoring campaign on the TeV binary LS I +61 303 has been performed utilizing >300 GeV observations with VERITAS along with monitoring in the 0.2-10 keV band by RXTE and Swift between September 2006 and…

Astrophysics · Physics 2019-08-13 A. W. Smith

Simultaneous X-Ray and TeV Gamma-Ray Observations of the TeV Blazar Markarian 421 during February and May 2000

In this paper we present the results of simultaneous observations of the TeV blazar Markarian 421 (Mrk 421) at X-ray and TeV Gamma-ray energies with the Rossi X-Ray Timing Explorer (RXTE) and the stereoscopic Cherenkov Telescope system of…

Astrophysics · Physics 2009-11-06 H. Krawczynski , R. Sambruna , A. Kohnle , P. S. Coppi , The HEGRA Collaboration , F. Aharonian

Time-resolved multiwavelength observations of the blazar VER J0521+211 from radio to gamma-ray energies

VER J0521+211 (RGB J0521.8+2112) is one of the brightest and most powerful blazars detected in the TeV gamma-ray regime. It is located at a redshift of z=0.108 and since its discovery in 2009, VER J0521+211 has exhibited an average TeV flux…

High Energy Astrophysical Phenomena · Physics 2019-08-15 Heike Prokoph , Paolo Da Vela , Cornelia Schultz