Now showing items 1-10 of 12

    • Characterising the long-term variability of blazars in leptonic models 

      Thiersen, Hannes; Zacharias, Michael; Böttcher, Markus (MDPI, 2019)
      Most research on blazar variability focuses on individual flares to explain acceleration and radiation mechanisms and improve on current models. These short-time events (being minutes, hours, or days) might not be ...
    • The fourth catalog of active galactic nuclei detected by the Fermi large area telescope 

      Ajello, M.; Kreter, M.; Axelsson, M.; Ballet, J.; Barbiellini, G. (IOP, 2020)
      The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains $2863$ objects located at high Galactic ...
    • H.E.S.S. monitoring of PKS 2155-304 in 2015 and 2016 

      Wierzcholska, Alicja; Zacharias, Michael; Jankowsky, Felix; Wagner, Stefan (MDPI, 2019)
      PKS 2155-304 is one of the brightest blazar located in Southern Hemisphere, monitored with H.E.S.S. since the first light of the experiment. Here we report multiwavelength monitoring observations collected during the ...
    • Impact of ordered and disordered magnetic fields on multiwavelength emission of blazars 

      Joshi, Manasvita; Böttcher, Markus; Marsher, Alan P. (IOP Publishing, 2020)
      We present a detailed analysis of the effects of magnetic field topology on the spectral energy distribution (SED) and spectral variability patterns (SVPs) of blazars. In order to study these effects, we have extended our ...
    • The long-lasting activity in the flat spectrum radio quasar (FSRQ) CTA 102 

      Zacharias, Michael; Böttcher, Markus; Jankowsky, Felix; Lenain, Jean-Philippe; Wagner, Stefan J. (MDPI, 2019)
      The flat spectrum radio quasar CTA 102 ( z=1.032 ) went through a tremendous phase of variability. Since early 2016 the gamma-ray flux level has been significantly higher than in previous years. It was topped by a four ...
    • Millimeter-wave monitoring of active galactic nuclei with the Africa millimetre telescope 

      Backes, Michael; Böttcher, Markus; Falcke, Heino (MDPI, 2019)
      Active galactic nuclei are the dominant sources of gamma rays outside our galaxy and are also candidates for the source of ultra-high energy cosmic rays. In addition to being emitters of broad-band non-thermal radiation ...
    • Multi-wavelength variability signatures of relativistic shocks in blazar jets 

      Böttcher, Markus; Baring, Matthew G. (IOP Publishing, 2019)
      Mildly relativistic shocks that are embedded in colliding magnetohydrodynamic flows are prime sites for relativistic particle acceleration and the production of strongly variable, polarized multi-wavelength emission from ...
    • New hard-TeV extreme blazars detected with the MAGIC telescopes 

      Acciari, V.A.; Arcaro, C.; Ansoldi, S.; Antonelli, L.A.; Arbet Engels, A. (IOP, 2020)
      Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 ...
    • Optical observations reveal strong evidence for high-energy neutrino progenitor 

      Lipunov, V.M.; Böttcher, M.; Kornilov, V.G.; Zhirkov, V.; Gorbovskoy, E. (IOP Publishing, 2020)
      We present the earliest astronomical observation of a high-energy neutrino error box of which the variability was discovered after high-energy-neutrino detection. The one robotic telescope of the MASTER global international ...
    • Optical variability modelling of newly identified blazars and blazar candidates behind Magellanic clouds 

      Zywucka, Natalia; Böttcher, Markus; Tarnopolski, Mariusz; Stawarz, Lukasz; Marchenko, Volodymyr (Sissa Medialab, 2019)
      We present results of a variability study in the optical band of 44 newly identified blazar candidates behind the Magellanic Clouds. Our sample contains 27 flat spectrum radio quasars (FSRQs) and 17 BL Lacertae objects (BL ...