Browsing by Author "Böttcher, M."

Now showing items 1-20 of 65

    • The 72-h WEBT microvariability observation of blazar S5 0716+714 in 2009 

      Bhatta, G.; Böttcher, M.; Webb, J.R.; Hollingsworth, H.; Dhalla, S. (EDP Sciences, 2013)
      Context. The international Whole Earth Blazar Telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This ...

    • Acceleration of petaelectronvolt protons in the Galactic Centre 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Spanier, F.; Sushch, I.; Venter, C.; Davids, I.D.; H.E.S.S. Collaboration (Nature Publishing Group, 2016)
      Galactic cosmic rays reach energies of at least a few petaelectronvolts1 (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of ...

    • Anisotropy and polarization effects in blazar emission 

      Tisang, Motseothata (North-West University (South Africa), 2023-10)
      Blazars are radio-loud (RL) active galactic nuclei (AGNs) whose relativistic jets are directed at us. These sources are observed to have spectral energy distributions (SEDs) with two broad-humped components, significant ...

    • Applying Monte Carlo methods to model multi-wavelength emission of RMHD jet simulations. 

      Van der Westhuizen, I.P.; Böttcher, M.; Van Soelen, B.; Meintjes, P.J. (Sissa Medialab, 2019)
      Relativistic jets associated with active galactic nuclei (AGN) produce radiation over a large range of the electromagnetic spectrum. While relativistic magneto-hydrodynamic (RMHD) simulations have become a powerful tool ...

    • The awakening of BL Lacertae: observations by Fermi, Swift and the GASP-WEBT 

      Raiteri, C.M.; Böttcher, M.; Villata, M.; D'Ammando, F.; Larionov, V.M. (Oxford University Press, 2013)
      Since the launch of the Fermi satellite, BL Lacertae has been moderately active at γ-rays and optical frequencies until 2011 May, when the source started a series of strong flares. The exceptional optical sampling achieved ...

    • Centaurus A: hard X-ray and soft gamma-ray lightcurve correlation 

      Davids, I.D.; Böttcher, M.; Backes, M. (Sissa Medialab, 2017)
      Centaurus A (Cen A), powered by a 55 million solar mass supermassive black hole, has been intensively monitored in all accessible wavelength ranges of the electromagnetic spectrum. However, its gamma-ray flux, both in the ...

    • Characterising the Long-Term Variability in Blazars 

      Thiersen, Johannes Hendrik Erasmus (North-West University (South Africa), 2020)
      Most research on blazar variability focuses on individual ares to explain acceleration and radiation mechanisms and improve on current models. These short-time events (being minutes, hours, or days) might not be representative ...

    • Characterizing the γ-ray long-term variability of PKS 2155-304 with H.E.S.S. and Fermi-LAT 

      Abdalla, H.; Barnard, M.; Böttcher, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Seyffert, A.S.; Spanier, F.; Sushch, I.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; H.E.S.S. Collaboration (EDP Sciences, 2017)
      Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To ...

    • Constraints on an annihilation signal from a core of constant dark matter density around the Milky Way center with H.E.S.S. 

      Abramowski, A.; Böttcher, M.; Davids, I.D.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Spanier, F.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (American Physical Society, 2015)
      An annihilation signal of dark matter is searched for from the central region of the Milky Way. Data acquired in dedicated on-off observations of the Galactic center region with H.E.S.S. are analyzed for this purpose. No ...

    • Constraints on the emission region of 3C 279 during strong flares in 2014 and 2015 through VHE γ-ray observations with H.E.S.S. 

      Abdalla, H.; Arcaro, C.; Backes, M.; Barnard, M.; Böttcher, M.; Chand, T.; Chandra, S.; Ndiyavala, H.; Schutte, H.; Seyffert, A.S.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; Żywucka, N.; H.E.S.S. Collaboration (EDP Sciences, 2019)
      The flat spectrum radio quasar 3C 279 is known to exhibit pronounced variability in the high-energy (100 MeV <  E <  100 GeV) γ-ray band, which is continuously monitored with Fermi-LAT. During two periods of high activity ...

    • Discovery of a new TeV gamma-ray source: Ver J0521+211 

      Archambault, S.; Böttcher, M.; Arlen, T.; Aune, T.; Behera, B. (IOP Science, 2013)
      We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by the discovery of a cluster ...

    • Discovery of the hard spectrum VHE γ-ray source HESS J1641-463 

      Abramowski, A.; Böttcher, M.; Davids, I.D.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Spanier, F.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (IOP Publishing, 2014)
      This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641–463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641–463 remained unnoticed by the usual ...

    • Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301-243 with H.E.S.S. 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2013)
      The active galactic nucleus PKS 0301−243 (z = 0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV < E < 100 GeV) by Fermi/LAT. This paper reports on the discovery of PKS 0301−243 ...

    • Event reconstruction for KM3NeT/ORCA using convolutional neural networks 

      Aiello, S.; Böttcher, M.; Kreter, M.; Zywucka, N. (IOP Publishing, 2020)
      The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of ...

    • First detection of the Crab Nebula at TeV energies with a Cherenkov telescope in a dual-mirror Schwarzschild-Couder configuration: the ASTRI-Horn telescope 

      Lombardi, S.; Böttcher, M.; Catalano, O.; Scuderi, S.; Antonelli, L.A. (EDP Sciences, 2020)
      We report on the first detection of very high-energy gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. This result has been achieved by means of the ...

    • First limits on the very-high energy gamma-ray afterglow emission of a fast radio burst. 

      Abdalla, H.; Barnard, M.; Böttcher, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Richter, S.; Seyffert, A.S.; Spanier, F.; Sushch, I.; Van der Walt, D.J.; Venter, C.; Van Rensburg, C.; Wadiasingh, Z.; H.E.S.S. Collaboration (EDP Sciences, 2017)
      Aims. Following the detection of the fast radio burst FRB150418 by the SUPERB project at the Parkes radio telescope, we aim to search for very-high energy gamma-ray afterglow emission. Methods. Follow-up observations in ...

    • Gamma-ray blazar spectra with H.E.S.S. II mono analysis: the case of PKS 2155-304 and PG 1553+113 

      Abdalla, H.; Barnard, M.; Böttcher, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Seyffert, A.S.; Spanier, F.; Sushch, I.; Van der Walt, D.J.; Venter, C.; Wadiasingh, Z.; H.E.S.S. Collaboration (EDP Sciences, 2017)
      Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment’s sensitivityto lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with ...

    • Gamma-ray observational properties of TeV-detected blazars 

      Senturk, G.D.; Böttcher, M.; Errando, M.; Mukherjee, R. (IOP Science, 2013)
      The synergy between the Fermi-LAT and ground-based Cherenkov telescope arrays gives us the opportunity for the first time to characterize the high-energy emission from blazars over 5 decades in energy, from 100 MeV to 10 ...

    • gSeaGen: the KM3NeT GENIE-based code for neutrino telescopes 

      Aiello, S.; Böttcher, M.; Kreter, M.; Rabyang, O.; Zywucka, N. (Elsevier, 2020)
      The gSeaGen code is a GENIE-based application developed to efficiently generate high statistics samples of events, induced by neutrino interactions, detectable in a neutrino telescope. The gSeaGen code is able to generate ...

    • H.E.S.S. and Fermi-LAT observations of PSR B1259-63/LS 2883 during its 2014 and 2017 periastron passages 

      Abdalla, H.; Arcara, C.; Backes, M.; Barnard, M.; Böttcher, M.; Chand, T.; Chandra, S.; Kreter, M.; Ndiyavala, H.; Schutte, H.; Seyffert, A.S.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; Żywucka, N.; Fermi LAT; H.E.S.S. Collaboration (EDP Sciences, 2020)
      Context. PSR B1259–63/LS 2883 is a gamma-ray binary system consisting of a pulsar in an eccentric orbit around a bright Oe stellar-type companion star that features a dense circumstellar disc. The bright broad-band emission ...