Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-37044 Wissenschaftlicher Artikel Abdo, A. A.; Ackermann, Margit; Ajello, M.; Allafort, A. J.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K. C.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Brandt, T. J.; Bregeon, Johan; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, Svenja; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Celik, O.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, Jan; Cutini, S.; Dermer, C. D.; de Palma, F.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guillemot, L.; Guiriec, S.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Johannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knoedlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S. -H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, Mario Nicola; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pavlidou, V.; Pearson, T. J.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Raino, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Richards, J. L.; Ripken, J.; Ritz, S.; Roth, M.; Sadrozinski, H. F. -W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgro, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, L.; Stevenson, M.; Strickman, M. S.; Sokolovsky, K. V.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Aleksic, J.; Antonelli, L. A.; Antoranz, P.; Backes, Michael; Barrio, J. A.; Gonzalez, J. Becerra; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch Bigas, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, Pol; Tridon, D. Borla; Bosch-Ramon, Valentin; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Dazzi, F.; de Angelis, A.; del Pozo, E. De Cea; De Lotto, B.; De Maria, M.; De Sabata, F.; Mendez, C. Delgado; Ortega, A. Diago; Doert, M.; Dominguez, A.; Prester, Dijana Dominis; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Lopen, R. J. Garcia; Garczarczyk, M.; Gaug, M.; Giavitto, G.; Godinovi, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Hoehne-Moench, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Kraehenbuehl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Lopez, M.; Lorenz, E.; Majumdar, P.; Makariev, E.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martinez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldon, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, J.; Pochon, J.; Moroni, P. G. Prada; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, T.; Reinthal, R.; Rhode, W.; Ribo, M.; Rico, J.; Rissi, M.; Ruegamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sanchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpaa, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L. O.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Tescaro, D.; Teshima, M.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; Acciari, V. A.; Arlen, T.; Aune, T.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Huang, D.; Hui, C. M.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Ong, R.; Otte, N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Rovero, A. C.; Schroedter, M.; Sembroski, G. H.; Senturk, G. D.; Steele, D.; Swordy, S. P.; Tesic, G.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wood, M.; Zitzer, B.; Villata, M.; Raiteri, C. M.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Blinov, D. A.; Calcidese, P.; Chen, W. P.; Efimova, N. V.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lahteenmaki, A.; Larionov, V. M.; Larionova, E. G.; Larionova, L. V.; Ligustri, R.; Morozova, D. A.; Nikolashvili, M. G.; Sigua, L. A.; Troitsky, I. S.; Angelakis, E.; Capalbi, M.; Carraminana, A.; Carrasco, L.; Cassaro, P.; de la Fuente, E.; Gurwell, M. A.; Kovalev, Y. Y.; Kovalev, Yu. A.; Krichbaum, T. P.; Krimm, H. A.; Leto, Paolo; Lister, M. L.; Maccaferri, G.; Moody, J. W.; Mori, Y.; Nestoras, I.; Orlati, A.; Pagani, C.; Pace, C.; Pearson, R.; Perri, M.; Piner, B. G.; Pushkarev, A. B.; Ros, E.; Sadun, A. C.; Sakamoto, T.; Tornikoski, M.; Yatsu, Y.; Zook, A. Insights into the high-energy gamma-Ray emission of markarian 501 fromextensive multifrequency observations in the fermi era We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size less than or similar to 0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (similar or equal to 10(44) erg s(-1)) constitutes only a small fraction (similar to 10(-3)) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. Bristol IOP Publ. Ltd. 2011 26 The astrophysical journal : an international review of spectroscopy and astronomical physics 727 2 10.1088/0004-637X/727/2/129 Institut für Physik und Astronomie OPUS4-38516 Wissenschaftlicher Artikel Furniss, A.; Noda, K.; Boggs, S.; Chiang, J.; Christensen, F.; Craig, W.; Giommi, P.; Hailey, C.; Harisson, F.; Madejski, G.; Nalewajko, K.; Perri, M.; Stern, D.; Urry, M.; Verrecchia, F.; Zhang, W.; Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; de Almeida, U. Barres; Barrio, J. A.; Becerra Gonzalez, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch Bigas, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Ona Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Prester, Dijana Dominis; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernandez-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; Garcia Lopez, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinovic, N.; Gonzalez Munoz, A.; Guberman, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kellermann, H.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; Lopez, M.; Lopez-Coto, R.; Lopez-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martinez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribo, M.; Rico, J.; Garcia, J. Rodriguez; Saito, T.; Saito, K.; Satalecka, K.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpaa, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Will, M.; Zanin, R.; Archer, A.; Benbow, W.; Bird, R.; Biteau, Jonathan; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, Xuhui; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Gerard, L.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hakansson, Nils; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Park, N.; Petry, D.; Pohl, Martin; Popkow, A.; Ragan, K.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, Igor O.; Tucci, J. V.; Tyler, J.; Vassiliev, V. V.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, Alina; Williams, D. A.; Zitzer, B.; Vince, O.; Fuhrmann, L.; Angelakis, E.; Karamanavis, V.; Myserlis, I.; Krichbaum, T. P.; Zensus, J. A.; Ungerechts, H.; Sievers, A.; Bachev, R.; Boettcher, Markus; Chen, W. P.; Damljanovic, G.; Eswaraiah, C.; Guver, T.; Hovatta, T.; Hughes, Z.; Ibryamov, S. I.; Joner, M. D.; Jordan, B.; Jorstad, S. G.; Joshi, M.; Kataoka, J.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lahteenmaki, A.; Latev, G.; Lin, H. C.; Larionov, V. M.; Mokrushina, A. A.; Morozova, D. A.; Nikolashvili, M. G.; Raiteri, C. M.; Ramakrishnan, V.; Readhead, A. C. R.; Sadun, A. C.; Sigua, L. A.; Semkov, E. H.; Strigachev, A.; Tammi, J.; Tornikoski, M.; Troitskaya, Y. V.; Troitsky, I. S.; Villata, M. First NuSTAR observations of MRK 501 within a radio to TeV multi-instrument campaign We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 2013 April 1 and August 10, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby BL Lac object was observed in both a quiescent and an elevated state. The broadband campaign includes observations with NuSTAR, MAGIC, VERITAS, the Fermi Large Area Telescope, Swift X-ray Telescope and UV Optical Telescope, various ground-based optical instruments, including the GASP-WEBT program, as well as radio observations by OVRO, Metsahovi, and the F-Gamma consortium. Some of the MAGIC observations were affected by a sand layer from the Saharan desert, and had to be corrected using event-by-event corrections derived with a Light Detection and Ranging (LIDAR) facility. This is the first time that LIDAR information is used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for the current and future ground-based gamma-ray instruments. The NuSTAR instrument provides unprecedented sensitivity in hard X-rays, showing the source to display a spectral energy distribution (SED) between 3 and 79 keV consistent with a log-parabolic spectrum and hard X-ray variability on hour timescales. None (of the four extended NuSTAR observations) show evidence of the onset of inverse-Compton emission at hard X-ray energies. We apply a single-zone equilibrium synchrotron self-Compton (SSC) model to five simultaneous broadband SEDs. We find that the SSC model can reproduce the observed broadband states through a decrease in the magnetic field strength coinciding with an increase in the luminosity and hardness of the relativistic leptons responsible for the high-energy emission. Bristol IOP Publ. Ltd. 2015 22 The astrophysical journal : an international review of spectroscopy and astronomical physics 812 1 10.1088/0004-637X/812/1/65 Institut für Physik und Astronomie OPUS4-47134 Wissenschaftlicher Artikel Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Gonzalez, J. Becerra; Bednarek, W.; Bernardini, E.; Berti, A.; Bhattacharyya, W.; Blanch, O.; Bonnoli, G.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colak, S. M.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.; Delgado, Jose Miguel Martins; Di Pierro, F.; Doert, M.; Dominguez, A.; Prester, D. Dominis; Doro, M.; Glawion, D. Eisenacher; Engelkemeier, M.; Ramazani, V. Fallah; Fernandez-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; Lopez, R. J. Garcia; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinovic, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuvezdic, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; Lopez, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Maraschi, L.; Mariotti, M.; Martinez, M.; Mazin, D.; Menzel, U.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Nagayoshi, T.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogues, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Ribo, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Shore, S. N.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Teshima, M.; Torres-Alba, N.; Treves, A.; Tsujimoto, S.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Zaric, D.; Arbet-Engels, A.; Baack, D.; Balbo, M.; Biland, A.; Blank, M.; Bretz, T.; Bruegge, K.; Bulinski, M.; Buss, J.; Dmytriiev, A.; Dorner, D.; Einecke, S.; Elsaesser, D.; Herbst, T.; Hildebrand, D.; Kortmann, L.; Linhoff, L.; Mahlke, M.; Mannheim, K.; Mueller, S. A.; Neise, D.; Neronov, A.; Noethe, M.; Oberkirch, J.; Paravac, A.; Rhode, W.; Schleicher, B.; Schulz, F.; Sedlaczek, K.; Shukla, A.; Sliusar, V.; Walter, R.; Archer, A.; Benbow, W.; Bird, R.; Brose, Robert; Buckley, J. H.; Bugaev, V.; Christiansen, J. L.; Cui, W.; Daniel, M. K.; Falcone, A.; Feng, Q.; Finley, J. P.; Gillanders, G. H.; Gueta, O.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Huetten, M.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pichel, A.; Pohl, Martin; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Sushch, Iurii; Tyler, J.; Wakely, S. P.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Wilhel, A.; Williams, D. A.; Williamson, T. J.; Zitzer, B.; Perri, M.; Verrecchia, F.; Leto, C.; Villata, M.; Raiteri, C. M.; Jorstad, S. G.; Larionov, V. M.; Blinov, D. A.; Grishina, T. S.; Kopatskaya, E. N.; Larionova, E. G.; Nikiforova, A. A.; Morozova, D. A.; Troitskaya, Yu. V.; Troitsky, I. S.; Kurtanidze, O. M.; Nikolashvili, M. G.; Kurtanidze, S. O.; Kimeridze, G. N.; Chigladze, R. A.; Strigachev, A.; Sadun, A. C. Extreme HBL behavior of Markarian 501 during 2012 Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Results. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of similar to 0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was similar to 3 CU, and the peak of the high-energy spectral component was found to be at similar to 2 TeV. Both the X-ray and VHE gamma-ray spectral slopes were measured to be extremely hard, with spectral indices <2 during most of the observing campaign, regardless of the X-ray and VHE flux. This study reports the hardest Mrk 501 VHE spectra measured to date. The fractional variability was found to increase with energy, with the highest variability occurring at VHE. Using the complete data set, we found correlation between the X-ray and VHE bands; however, if the June 9 flare is excluded, the correlation disappears (significance <3 sigma) despite the existence of substantial variability in the X-ray and VHE bands throughout the campaign. Conclusions. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency-peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The data set acquired shows that the broadband spectral energy distribution (SED) of Mrk 501, and its transient evolution, is very complex, requiring, within the framework of synchrotron self-Compton (SSC) models, various emission regions for a satisfactory description. Nevertheless the one-zone SSC scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behavior seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays. Les Ulis EDP Sciences 2018 23 Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO) 620 10.1051/0004-6361/201833704 Institut für Physik und Astronomie