TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008

V. A. Acciari, E. Aliu, T. Arlen, T. Aune, M. Beilicke, W. Benbow, D. Boltuch, S. M. Bradbury, J. H. Buckley, V. Bugaev, K. Byrum, A. Cannon, A. Cesarini, L. Ciupik, W. Cui, R. Dickherber, C. Duke, A. Falcone, J. P. Finley, G. FinneganL. Fortson, A. Furniss, N. Galante, D. Gall, G. H. Gillanders, S. Godambe, J. Grube, R. Guenette, G. Gyuk, D. Hanna, J. Holder, C. M. Hui, T. B. Humensky, A. Imran, P. Kaaret, N. Karlsson, M. Kertzman, D. Kieda, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, G. Maier, S. McArthur, M. McCutcheon, P. Moriarty, R. A. Ong, A. N. Otte, M. Ouellette, D. Pandel, J. S. Perkins, A. Pichel, M. Pohl, J. Quinn, K. Ragan, L. C. Reyes, P. T. Reynolds, E. Roache, H. J. Rose, A. C. Rovero, M. Schroedter, G. H. Sembroski, G. D. Senturk, D. Steele, S. P. Swordy, M. Theiling, S. Thibadeau, A. Varlotta, V. V. Vassiliev, S. Vincent, R. G. Wagner, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, T. Weisgarber, D. A. Williams, S. Wissel, M. Wood, B. Zitzer, A. Garson III, K. Lee, A.~C. Sadun, M. Carini, D. Barnaby, K. Cook, J. Maune, A. Pease, S. Smith, R. Walters, A. Berdyugin, E. Lindfors, K. Nilsson, M. Pasanen, J. Sainio, A. Sillanpaa, L. O. Takalo, C. Villforth, T. Montaruli, M. Baker, A. Lahteenmaki, M. Tornikoski, T. Hovatta, E. Nieppola, H. D. Aller, M. F. Aller

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92 Citations (Scopus)


We report on TeV γ-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10 m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV γ-ray fluxes and energy spectra with unprecedented accuracy where Mrk 421 was detected in each of the pointings. A total of 47.3 hr of VERITAS and 96 hr of Whipple 10 m data were acquired between 2006 January and 2008 June. We present the results of a study of the TeV γ-ray energy spectra as a function of time and for different flux levels. On 2008 May 2 and 3, bright TeV γ-ray flares were detected with fluxes reaching the level of 10 Crab. The TeV γ-ray data were complemented with radio, optical, and X-ray observations, with flux variability found in all bands except for the radio wave band. The combination of the Rossi X-ray Timing Explorer and Swift X-ray data reveal spectral hardening with increasing flux levels, often correlated with an increase of the source activity in TeV γ-rays. Contemporaneous spectral energy distributions were generated for 18 nights, each of which are reasonably described by a one-zone synchrotron self-Compton model.
Original languageEnglish
Pages (from-to)25
Number of pages1
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2011

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