FIRST NuSTAR OBSERVATIONS OF MRK 501 WITHIN A RADIO TO TeV MULTI-INSTRUMENT CAMPAIGN
- Department of Physics, Stanford University, Stanford, CA 94305 (United States)
- Max-Planck-Institut für Physik, D-80805 München (Germany)
- Space Science Laboratory, University of California, Berkeley, CA 94720 (United States)
- Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
- DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
- Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)
- ASI Science Data Center (ASDC), Italian Space Agency (ASI), Via del Politecnico snc, Rome (Italy)
- Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
- Cahill Center for Astronomy and Astrophysics, Caltech, Pasadena, CA 91125 (United States)
- INAF-OAR, Via Frascati 33, I-00040 Monte Porzio Catone (RM) (Italy)
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
- Yale Center for Astronomy and Astrophysics, Physics Department, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States)
- NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- ETH Zurich, CH-8093 Zurich (Switzerland)
- Università di Udine, and INFN Trieste, I-33100 Udine (Italy)
- INAF National Institute for Astrophysics, I-00136 Rome (Italy)
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.
- OSTI ID:
- 22525265
- Journal Information:
- Astrophysical Journal, Vol. 812, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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