FIRST NuSTAR OBSERVATIONS of MRK 501 WITHIN A RADIO to TeV MULTI-INSTRUMENT CAMPAIGN

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.; Barres De Almeida, U.; A. Barrio, J.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, 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 Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernández Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, 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.; López, M.; López Coto, R.; López Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, 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.; PRADA MORONI, PIER GIORGIO; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Saito, K.; Satalecka, K.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, STEVEN NEIL; Sillanpä, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, 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, J.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; 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.; Håkansson, N.; 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.; O'Faoláin De Bhróithe, A.; Ong, R. A.; Park, N.; Petry, D.; Pohl, M.; 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, I.; Tucci, J. V.; Tyler, J.; Vassiliev, V. V.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; 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.; Böttcher, M.; Chen, W. P.; Damljanovic, G.; Eswaraiah, C.; Güver, 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.; Lähteenmäki, A.; Latev, G.; Lin, H. C.; Larionov, V. M.; Mokrushina, A. A.; Morozova, D. A.; Nikolashvili, M. G.; Raiteri, C. M.; Ramakrishnan, V.; A. C., R. Readhead; Sadun, A. C.; Sigua, L. A.; Semkov, E. H.; Strigachev, A.; Tammi, J.; Tornikoski, M.; Troitskaya, Y. V.; Troitsky, I. S.; Villata, M.

doi:10.1088/0004-637X/812/1/65

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, Metsähovi, 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.