TeV AND MULTI-WAVELENGTH OBSERVATIONS OF Mrk 421 IN 2006-2008

V. A. Acciari(Center for Astrophysics Harvard & Smithsonian), E. Aliu(Columbia University), T. Arlen(University of California, Los Angeles), T. Aune(University of California, Santa Cruz), M. Beilicke(Washington University in St. Louis), W. Benbow(Center for Astrophysics Harvard & Smithsonian), D. Boltuch(University of Delaware), S. M. Bradbury(University of Leeds), J. H. Buckley(Washington University in St. Louis), V. Bugaev(Washington University in St. Louis), K. Byrum(Argonne National Laboratory), A. Cannon(University College Dublin), A. Cesarini(Ollscoil na Gaillimhe – University of Galway), L. Ciupik(Adler Planetarium), Wei Cui(Purdue University West Lafayette), R. Dickherber(Washington University in St. Louis), C. Duke(Grinnell College), A. Falcone(Pennsylvania State University), J. P. Finley(Purdue University West Lafayette), G. Finnegan(University of Utah), L. Fortson(Adler Planetarium), A. Furniss(University of California, Santa Cruz), N. Galante(Center for Astrophysics Harvard & Smithsonian), D. Gall(University of Iowa), G. H. Gillanders(Ollscoil na Gaillimhe – University of Galway), S. Godambe(University of Utah), J. Grube(Adler Planetarium), R. Guénette(McGill University), G. Gyuk(Adler Planetarium), D. Hanna(McGill University), J. Holder(University of Delaware), C. M. Hui(University of Utah), T. B. Humensky(Fermi National Accelerator Laboratory), Asif Imran(Iowa State University), P. Kaaret(University of Iowa), N. Karlsson(Adler Planetarium), M. Kertzman(DePauw University), D. Kieda(University of Utah), A. Konopelko(Pittsburg State University), H. Krawczynski(Washington University in St. Louis), F. Krennrich(Iowa State University), M. J. Lang(Ollscoil na Gaillimhe – University of Galway), G. Maier(McGill University), S. McArthur(Washington University in St. Louis), M. McCutcheon(McGill University), P. Moriarty(Galway-Mayo Institute of Technology), R. A. Ong(University of California, Los Angeles), A. N. Otte(University of California, Santa Cruz), M. Ouellette(California Polytechnic State University), D. Pandel(University of Iowa), J. S. Perkins(Center for Astrophysics Harvard & Smithsonian), A. Pichel(Institute of Astronomy and Space Physics), M. Pohl(Iowa State University), J. Quinn(University College Dublin), K. Ragan(McGill University), L. C. Reyes(University of Chicago), P. T. Reynolds(Munster Technological University), E. Roache(Center for Astrophysics Harvard & Smithsonian), H. J. Rose(University of Leeds), Adrián Rovero(Institute of Astronomy and Space Physics), M. Schroedter(Iowa State University), G. H. Sembroski(Purdue University West Lafayette), G. D. Şentürk(Columbia University), D. Steele(Adler Planetarium), S. P. Swordy(Fermi National Accelerator Laboratory), M. Theiling(Center for Astrophysics Harvard & Smithsonian), S. Thibadeau(Washington University in St. Louis), A. Varlotta(Purdue University West Lafayette), V. V. Vassiliev(University of California, Los Angeles), S. Vincent(University of Utah), R. G. Wagner(Argonne National Laboratory), S. P. Wakely(Fermi National Accelerator Laboratory), J. E. Ward(University College Dublin), T. C. Weekes(Center for Astrophysics Harvard & Smithsonian), A. J. Weinstein(University of California, Los Angeles), T. Weisgarber(Fermi National Accelerator Laboratory), D. A. Williams(University of California, Santa Cruz), Stephanie Wissel(Fermi National Accelerator Laboratory), M. Wood(University of California, Los Angeles), B. Zitzer(Purdue University West Lafayette), A. Garson(Washington University in St. Louis), K. Lee(Washington University in St. Louis), —BRT NMS A. C. Sadun(University of Colorado Denver), —Bell M. Carini(Western Kentucky University), D. Barnaby(Western Kentucky University), K. Cook(Western Kentucky University), J. Maune(Western Kentucky University), A. Pease(Western Kentucky University), S. Smith(Western Kentucky University), Richard Walters(Western Kentucky University), —Tuorla KVA A. Berdyugin(University of Turku), E. Lindfors(University of Turku), K. Nilsson(University of Turku), M. Pasanen(University of Turku), J. Sainio(University of Turku), A. Sillanpää(University of Turku), L. O. Takalo(University of Turku), C. Villforth(University of Turku), —WIYN T. Montaruli(University of Wisconsin–Madison), M. Baker(University of Wisconsin–Madison), —Metsähovi A. Lahteenmaki(Aalto University), M. Tornikoski(Aalto University), T. Hovatta(Aalto University), E. Nieppola(Aalto University), —UMRAO H. D. Aller(University of Michigan), M. F. Aller(University of Michigan)
The Astrophysical Journal
August 10, 2011
10.1088/0004-637x/738/1/25
Cited by 153Open Access
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Abstract

We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV gamma-ray fluxes and energy spectra with unprecedented accuracy where Mrk 421 was detected in each of the pointings. A total of 47.3 hrs of VERITAS and 96 hrs of Whipple 10m data were acquired between January 2006 and June 2008. We present the results of a study of the TeV gamma-ray energy spectra as a function of time, and for different flux levels. On May 2nd and 3rd, 2008, bright TeV gamma-ray flares were detected with fluxes reaching the level of 10 Crab. The TeV gamma-ray data were complemented with radio, optical, and Xray observations, with flux variability found in all bands except for the radio waveband. The combination of the RXTE and Swift X-ray data reveal spectral hardening with increasing flux levels, often correlated with an increase of the source activity in TeV gamma-rays. Contemporaneous spectral energy distributions were generated for 18 nights, each of which are reasonably described by a one-zone SSC model.

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