@article {2012ApJ...746..151A,
	title = {{The 2010 Very High Energy {$\gamma$}-Ray Flare and 10 Years of Multi-wavelength Observations of M 87}},
	journal = {The Astrophysical Journal},
	volume = {746},
	year = {2012},
	month = {feb},
	pages = {151},
	abstract = {The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3 - 6) {\times} 10$^{9}$ M $_{\&sun;}$) provides a unique opportunity to investigate the origin of very high energy (VHE; E {\gt} 100 GeV) {$\gamma$}-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE {$\gamma$}-ray emitter since 2006. The VHE {$\gamma$}-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE {$\gamma$}-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of {$\tau$}$^{rise}$ $_{d}$ = (1.69 {\plusmn} 0.30) days and {$\tau$}$^{decay}$ $_{d}$ = (0.611 {\plusmn} 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (\~{}day), peak fluxes ({$\Phi$}$_{>0.35 TeV}$ \~{}= (1-3) {\times} 10$^{-11}$ photons cm$^{-2}$ s$^{-1}$), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken \~{}3 days after the peak of the VHE {$\gamma$}-ray emission reveal an enhanced flux from the core (flux increased by factor \~{}2; variability timescale {\l}t}2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE {$\gamma$}-ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: 2002-2009). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE {$\gamma$}-ray emission from M 87 are reviewed in the light of the new data.},
	keywords = {galaxies: active, galaxies: individual: M 87, galaxies: jets, galaxies: nuclei, gamma rays: galaxies, radiation mechanisms: non-thermal},
	doi = {10.1088/0004-637X/746/2/151},
	url = {http://adsabs.harvard.edu/abs/2012ApJ...746..151A},
	author = {Abramowski, A. and Acero, F. and Aharonian, F. and Akhperjanian, A.~G. and Anton, G. and Balzer, A. and Barnacka, A. and Barres de Almeida, U. and Becherini, Y. and Becker, J. and Behera, B. and Bernl{\"o}hr, K. and Birsin, E. and Biteau, J. and Bochow, A. and Boisson, C. and Bolmont, J. and Bordas, P. and Brucker, J. and Brun, F. and Brun, P. and Bulik, T. and B{\"u}sching, I. and Carrigan, S. and Casanova, S. and Cerruti, M. and Chadwick, P.~M. and Charbonnier, A. and Chaves, R.~C.~G. and Cheesebrough, A. and Clapson, A.~C. and Coignet, G. and Cologna, G. and Conrad, J. and Dalton, M. and Daniel, M.~K. and Davids, I.~D. and Degrange, B. and Deil, C. and Dickinson, H.~J. and Djannati-Ata{\"\i}, A. and Domainko, W. and Drury, L.~O. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Egberts, K. and Eger, P. and Espigat, P. and Fallon, L. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandes, M.~V. and Fiasson, A. and Fontaine, G. and F{\"o}rster, A. and F{\"u}{\ss}ling, M. and Gallant, Y.~A. and Gast, H. and G{\'e}rard, L. and Gerbig, D. and Giebels, B. and Glicenstein, J.~F. and Gl{\"u}ck, B. and Goret, P. and G{\"o}ring, D. and H{\"a}ffner, S. and Hague, J.~D. and Hampf, D. and Hauser, M. and Heinz, S. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hinton, J.~A. and Hoffmann, A. and Hofmann, W. and Hofverberg, P. and Holler, M. and Horns, D. and Jacholkowska, A. and de Jager, O.~C. and Jahn, C. and Jamrozy, M. and Jung, I. and Kastendieck, M.~A. and Katarzy{\'n}ski, K. and Katz, U. and Kaufmann, S. and Keogh, D. and Khangulyan, D. and Kh{\'e}lifi, B. and Klochkov, D. and Klu{\'z}niak, W. and Kneiske, T. and Komin, N. and Kosack, K. and Kossakowski, R. and Laffon, H. and Lamanna, G. and Lennarz, D. and Lohse, T. and Lopatin, A. and Lu, C.-C. and Marandon, V. and Marcowith, A. and Masbou, J. and Maurin, D. and Maxted, N. and Mayer, M. and McComb, T.~J.~L. and Medina, M.~C. and M{\'e}hault, J. and Moderski, R. and Moulin, E. and Naumann, C.~L. and Naumann-Godo, M. and de Naurois, M. and Nedbal, D. and Nekrassov, D. and Nguyen, N. and Nicholas, B. and Niemiec, J. and Nolan, S.~J. and Ohm, S. and de O{\~n}a Wilhelmi, E. and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Paz Arribas, M. and Pedaletti, G. and Pelletier, G. and Petrucci, P.-O. and Pita, S. and P{\"u}hlhofer, G. and Punch, M. and Quirrenbach, A. and Raue, M. and Rayner, S.~M. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Rieger, F. and Ripken, J. and Rob, L. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C.~B. and Ruppel, J. and Sahakian, V. and Sanchez, D.~A. and Santangelo, A. and Schlickeiser, R. and Sch{\"o}ck, F.~M. and Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sheidaei, F. and Skilton, J.~L. and Sol, H. and Spengler, G. and Stawarz, {\L}. and Steenkamp, R. and Stegmann, C. and Stinzing, F. and Stycz, K. and Sushch, I. and Szostek, A. and Tavernet, J.-P. and Terrier, R. and Tluczykont, M. and Valerius, K. and van Eldik, C. and Vasileiadis, G. and Venter, C. and Vialle, J.~P. and Viana, A. and Vincent, P. and V{\"o}lk, H.~J. and Volpe, F. and Vorobiov, S. and Vorster, M. and Wagner, S.~J. and Ward, M. and White, R. and Wierzcholska, A. and Zacharias, M. and Zajczyk, A. and Zdziarski, A.~A. and Zech, A. and Zechlin, H.-S. and H.E.S.S.~Collaboration and Aleksi{\'c}, J. and Antonelli, L.~A. and Antoranz, P. and Backes, M. and Barrio, J.~A. and Bastieri, D. and Becerra Gonz{\'a}lez, J. and Bednarek, W. and Berdyugin, A. and Berger, K. and Bernardini, E. and Biland, A. and Blanch, O. and Bock, R.~K. and Boller, A. and Bonnoli, G. and Borla Tridon, D. and Braun, I. and Bretz, T. and Ca{\~n}ellas, A. and Carmona, E. and Carosi, A. and Colin, P. and Colombo, E. and Contreras, J.~L. and Cortina, J. and Cossio, L. and Covino, S. and Dazzi, F. and De Angelis, A. and De Cea del Pozo, E. and De Lotto, B. and Delgado Mendez, C. and Diago Ortega, A. and Doert, M. and Dom{\'\i}nguez, A. and Dominis Prester, D. and Dorner, D. and Doro, M. and Elsaesser, D. and Ferenc, D. and Fonseca, M.~V. and Font, L. and Fruck, C. and Garc{\'\i}a L{\'o}pez, R.~J. and Garczarczyk, M. and Garrido, D. and Giavitto, G. and Godinovi{\'c}, N. and Hadasch, D. and H{\"a}fner, D. and Herrero, A. and Hildebrand, D. and H{\"o}hne-M{\"o}nch, D. and Hose, J. and Hrupec, D. and Huber, B. and Jogler, T. and Klepser, S. and Kr{\"a}henb{\"u}hl, T. and Krause, J. and La Barbera, A. and Lelas, D. and Leonardo, E. and Lindfors, E. and Lombardi, S. and L{\'o}pez, M. and Lorenz, E. and Makariev, M. and Maneva, G. and Mankuzhiyil, N. and Mannheim, K. and Maraschi, L. and Mariotti, M. and Mart{\'\i}nez, M. and Mazin, D. and Meucci, M. and Miranda, J.~M. and Mirzoyan, R. and Miyamoto, H. and Mold{\'o}n, J. and Moralejo, A. and Munar, P. and Nieto, D. and Nilsson, K. and Orito, R. and Oya, I. and Paneque, D. and Paoletti, R. and Pardo, S. and Paredes, J.~M. and Partini, S. and Pasanen, M. and Pauss, F. and M. A. P{\'e}rez-Torres and Persic, M. and Peruzzo, L. and Pilia, M. and Pochon, J. and Prada, F. and Prada Moroni, P.~G. and Prandini, E. and Puljak, I. and Reichardt, I. and Reinthal, R. and Rhode, W. and Rib{\'o}, M. and Rico, J. and R{\"u}gamer, S. and Saggion, A. and Saito, K. and Saito, T.~Y. and Salvati, M. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schultz, C. and Schweizer, T. and Shayduk, M. and Shore, S.~N. and Sillanp{\"a}{\"a}, A. and Sitarek, J. and Sobczynska, D. and Spanier, F. and Spiro, S. and Stamerra, A. and Steinke, B. and Storz, J. and Strah, N. and Suri{\'c}, T. and Takalo, L. and Takami, H. and Tavecchio, F. and Temnikov, P. and Terzi{\'c}, T. and Tescaro, D. and Teshima, M. and Thom, M. and Tibolla, O. and Torres, D.~F. and Treves, A. and Vankov, H. and Vogler, P. and Wagner, R.~M. and Weitzel, Q. and Zabalza, V. and Zandanel, F. and Zanin, R. and MAGIC Collaboration and Arlen, T. and Aune, T. and Beilicke, M. and Benbow, W. and Bouvier, A. and Bradbury, S.~M. and Buckley, J.~H. and Bugaev, V. and Byrum, K. and Cannon, A. and Cesarini, A. and Ciupik, L. and Connolly, M.~P. and Cui, W. and Dickherber, R. and Duke, C. and Errando, M. and Falcone, A. and Finley, J.~P. and Finnegan, G. and Fortson, L. and Furniss, A. and Galante, N. and Gall, D. and Godambe, S. and Griffin, S. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Huan, H. and Hui, C.~M. and Kaaret, P. and Karlsson, N. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M.~J. and LeBohec, S. and Maier, G. and McArthur, S. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nu{\~n}ez, P.~D. and Ong, R.~A. and Orr, M. and Otte, A.~N. and Park, N. and Perkins, J.~S. and Pichel, A. and Pohl, M. and Prokoph, H. and Ragan, K. and Reyes, L.~C. and Reynolds, P.~T. and Roache, E. and Rose, H.~J. and Ruppel, J. and Schroedter, M. and Sembroski, G.~H. and \c Sent{\"u}rk, G.~D. and Telezhinsky, I. and Te\v si{\'c}, G. and Theiling, M. and Thibadeau, S. and Varlotta, A. and Vassiliev, V.~V. and Vivier, M. and Wakely, S.~P. and Weekes, T.~C. and Williams, D.~A. and Zitzer, B. and VERITAS Collaboration and Barres de Almeida, U. and Cara, M. and Casadio, C. and Cheung, C.~C. and McConville, W. and Davies, F. and Doi, A. and Giovannini, G. and Giroletti, M. and Hada, K. and Hardee, P. and Harris, D.~E. and Junor, W. and Kino, M. and Lee, N.~P. and Ly, C. and Madrid, J. and Massaro, F. and Mundell, C.~G. and Nagai, H. and Perlman, E.~S. and Steele, I.~A. and Walker, R.~C. and Wood, D.~L.}
}
@article {2011ApJ...736..131A,
	title = {{Fermi Large Area Telescope Observations of Markarian 421: The Missing Piece of its Spectral Energy Distribution}},
	journal = {The Astrophysical Journal},
	volume = {736},
	year = {2011},
	month = {aug},
	pages = {131},
	abstract = {We report on the {$\gamma$}-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) {$\gamma$}-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index {$\Gamma$} = 1.78 {\plusmn} 0.02 and average photon flux F({\gt} 0.3 GeV) = (7.23 {\plusmn} 0.16) {\times} 10$^{-8}$ ph cm$^{-2}$ s$^{-1}$. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor \~{}3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in {$\gamma$}-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.},
	keywords = {acceleration of particles, BL Lacertae objects: general, BL Lacertae objects: individual: Mrk 421, galaxies: active, gamma rays: general, radiation mechanisms: non-thermal},
	doi = {10.1088/0004-637X/736/2/131},
	url = {http://adsabs.harvard.edu/abs/2011ApJ...736..131A},
	author = {Abdo, A.~A. and Ackermann, M. and Ajello, M. and Baldini, L. and Ballet, J. and Barbiellini, G. and Bastieri, D. and Bechtol, K. and Bellazzini, R. and Berenji, B. and Blandford, R.~D. and Bloom, E.~D. and Bonamente, E. and Borgland, A.~W. and Bouvier, A. and Bregeon, J. and Brez, A. and Brigida, M. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G.~A. and Cameron, R.~A. and Cannon, A. and Caraveo, P.~A. and Carrigan, S. and Casandjian, J.~M. and Cavazzuti, E. and Cecchi, C. and {\c C}elik, {\"O}. and Charles, E. and Chekhtman, A. and Chiang, J. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Conrad, J. and Cutini, S. and De Angelis, A. and de Palma, F. and Dermer, C.~D. and Silva, E.~d.~C.~e. and Drell, P.~S. and Dubois, R. and Dumora, D. and Escande, L. and Favuzzi, C. and Fegan, S.~J. and Finke, J. and Focke, W.~B. and Fortin, P. and Frailis, M. and Fuhrmann, L. and Fukazawa, Y. and Fukuyama, T. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Georganopoulos, M. and Germani, S. and Giebels, B. and Giglietto, N. and Giommi, P. and Giordano, F. and Giroletti, M. and Glanzman, T. and Godfrey, G. and Grenier, I.~A. and Guiriec, S. and Hadasch, D. and Hayashida, M. and Hays, E. and Horan, D. and Hughes, R.~E. and J{\'o}hannesson, G. and Johnson, A.~S. and Johnson, W.~N. and Kadler, M. and Kamae, T. and Katagiri, H. and Kataoka, J. and Kn{\"o}dlseder, J. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S.-H. and Longo, F. and Loparco, F. and Lott, B. and Lovellette, M.~N. and Lubrano, P. and Madejski, G.~M. and Makeev, A. and Max-Moerbeck, W. and Mazziotta, M.~N. and McEnery, J.~E. and M{\'e}hault, J. and Michelson, P.~F. and Mitthumsiri, W. and Mizuno, T. and Monte, C. and Monzani, M.~E. and Morselli, A. and Moskalenko, I.~V. and Murgia, S. and Nakamori, T. and Naumann-Godo, M. and Nishino, S. and Nolan, P.~L. and Norris, J.~P. and Nuss, E. and Ohsugi, T. and Okumura, A. and Omodei, N. and Orlando, E. and Ormes, J.~F. and Ozaki, M. and Paneque, D. and Panetta, J.~H. and Parent, D. and Pavlidou, V. and Pearson, T.~J. and Pelassa, V. and Pepe, M. and Pesce-Rollins, M. and Pierbattista, M. and Piron, F. and Porter, T.~A. and Rain{\`o}, S. and Rando, R. and Razzano, M. and Readhead, A. and Reimer, A. and Reimer, O. and Reyes, L.~C. and Richards, J.~L. and Ritz, S. and Roth, M. and Sadrozinski, H.~F.-W. and Sanchez, D. and Sander, A. and Sgr{\`o}, C. and Siskind, E.~J. and Smith, P.~D. and Spandre, G. and Spinelli, P. and Stawarz, {\L}. and Stevenson, M. and Strickman, M.~S. and Suson, D.~J. and Takahashi, H. and Takahashi, T. and Tanaka, T. and Thayer, J.~G. and Thayer, J.~B. and Thompson, D.~J. and Tibaldo, L. and Torres, D.~F. and Tosti, G. and Tramacere, A. and Troja, E. and Usher, T.~L. and Vandenbroucke, J. and Vasileiou, V. and Vianello, G. and Vilchez, N. and Vitale, V. and Waite, A.~P. and Wang, P. and Wehrle, A.~E. and Winer, B.~L. and Wood, K.~S. and Yang, Z. and Yatsu, Y. and Ylinen, T. and Zensus, J.~A. and Ziegler, M. and Fermi LAT Collaboration and Aleksi{\'c}, J. and Antonelli, L.~A. and Antoranz, P. and Backes, M. and Barrio, J.~A. and Becerra Gonz{\'a}lez, J. and Bednarek, W. and Berdyugin, A. and Berger, K. and Bernardini, E. and Biland, A. and Blanch, O. and Bock, R.~K. and Boller, A. and Bonnoli, G. and Bordas, P. and Borla Tridon, D. and Bosch-Ramon, V. and Bose, D. and Braun, I. and Bretz, T. and Camara, M. and Carmona, E. and Carosi, A. and Colin, P. and Colombo, E. and Contreras, J.~L. and Cortina, J. and Covino, S. and Dazzi, F. and De Angelis, A. and De Cea del Pozo, E. and Delgado Mendez, C. and De Lotto, B. and De Maria, M. and De Sabata, F. and Diago Ortega, A. and Doert, M. and Dom{\'\i}nguez, A. and Dominis Prester, D. and Dorner, D. and Doro, M. and Elsaesser, D. and Ferenc, D. and Fonseca, M.~V. and Font, L. and Garc{\'\i}a L{\'o}pez, R.~J. and Garczarczyk, M. and Gaug, M. and Giavitto, G. and Godinovi, N. and Hadasch, D. and Herrero, A. and Hildebrand, D. and H{\"o}hne-M{\"o}nch, D. and Hose, J. and Hrupec, D. and Jogler, T. and Klepser, S. and Kr{\"a}henb{\"u}hl, T. and Kranich, D. and Krause, J. and La Barbera, A. and Leonardo, E. and Lindfors, E. and Lombardi, S. and L{\'o}pez, M. and Lorenz, E. and Majumdar, P. and Makariev, E. and Maneva, G. and Mankuzhiyil, N. and Mannheim, K. and Maraschi, L. and Mariotti, M. and Mart{\'\i}nez, M. and Mazin, D. and Meucci, M. and Miranda, J.~M. and Mirzoyan, R. and Miyamoto, H. and Mold{\'o}n, J. and Moralejo, A. and Nieto, D. and Nilsson, K. and Orito, R. and Oya, I. and Paoletti, R. and Paredes, J.~M. and Partini, S. and Pasanen, M. and Pauss, F. and Pegna, R.~G. and M. A. P{\'e}rez-Torres and Persic, M. and Peruzzo, J. and Pochon, J. and Prada, F. and Prada Moroni, P.~G. and Prandini, E. and Puchades, N. and Puljak, I. and Reichardt, T. and Rhode, W. and Rib{\'o}, M. and Rico, J. and Rissi, M. and R{\"u}gamer, S. and Saggion, A. and Saito, K. and Saito, T.~Y. and Salvati, M. and S{\'a}nchez-Conde, M. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schultz, C. and Schweizer, T. and Shayduk, M. and Shore, S.~N. and Sierpowska-Bartosik, A. and Sillanp{\"a}{\"a}, A. and Sitarek, J. and Sobczynska, D. and Spanier, F. and Spiro, S. and Stamerra, A. and Steinke, B. and Storz, J. and Strah, N. and Struebig, J.~C. and Suri{\'c}, T. and Takalo, L.~O. and Tavecchio, F. and Temnikov, P. and Terzi{\'c}, T. and Tescaro, D. and Teshima, M. and Vankov, H. and Wagner, R.~M. and Weitzel, Q. and Zabalza, V. and Zandanel, F. and Zanin, R. and MAGIC Collaboration and Villata, M. and Raiteri, C. and Aller, H.~D. and Aller, M.~F. and Chen, W.~P. and Jordan, B. and Koptelova, E. and Kurtanidze, O.~M. and L{\"a}hteenm{\"a}ki, A. and McBreen, B. and Larionov, V.~M. and Lin, C.~S. and Nikolashvili, M.~G. and Reinthal, R. and Angelakis, E. and Capalbi, M. and Carrami{\~n}ana, A. and Carrasco, L. and Cassaro, P. and Cesarini, A. and Falcone, A. and Gurwell, M.~A. and Hovatta, T. and Kovalev, Y.~A. and Kovalev, Y.~Y. and Krichbaum, T.~P. and Krimm, H.~A. and Lister, M.~L. and Moody, J.~W. and Maccaferri, G. and Mori, Y. and Nestoras, I. and Orlati, A. and Pace, C. and Pagani, C. and Pearson, R. and Perri, M. and Piner, B.~G. and Ros, E. and Sadun, A.~C. and Sakamoto, T. and Tammi, J. and Zook, A.}
}
