Now showing items 1-18 of 18

    • Characterizing the ?-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. (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 axionlike particles with H.E.S.S. from the irregularity of the PKS 2155-304 energy spectrum 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Sushch, I.; Venter, C.; Vorster, M. (APS, 2013)
      Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent ...
    • 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. (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 ...
    • First limits on the very-high energy gamma-ray afterglow emission of a fast radio burst. H.E.S.S. observations of FRB 150418 

      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. (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 ...
    • Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011 

      Abramowski, A.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2014)
      Context. About 40% of the observation time of the High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim of increasing the sample of known extragalactic very-high-energy ...
    • 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. (EDP Sciences, 2017)
      Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment’s sensitivity to lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with ...
    • HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312-423 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (Oxford Univ Press, 2013)
      A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ-rays from the blazar 1ES 1312−423, 2° away from the radio galaxy. With a differential flux at ...
    • HESS J1640-465: an exceptionally luminous TeV γ-ray supernova remnant 

      Abramowski, A.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M.; Böttcher, M. (Oxford Univ Press, 2014)
      The results of follow-up observations of the TeV γ-ray source HESS J1640−465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well described by an exponential ...
    • HESS J1818-154, a new composite supernova remnant discovered in TeV gamma rays and X-rays 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2014)
      Composite supernova remnants (SNRs) constitute a small subclass of the remnants of massive stellar explosions where non-thermal radiation is observed from both the expanding shell-like shock front and from a pulsar wind ...
    • Long-term monitoring of PKS2155-304 with ATOM and H.E.S.S.: investigation of optical/y-ray correlations in different spectral states 

      Abramowski, A.; Böttcher, M.; Davids, I.D.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Spanier, F.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2014)
      In this paper we report on the analysis of all the available optical and very high-energy y-ray (>200 GeV) data for the BL Lac object PKS 2155-304, collected simultaneously with the ATOM and H.E.S.S. telescopes from ...
    • Long-term TeV and X-ray observations of the gamma-ray binary HESS J0632+057 

      Abramowski, A.; Böttcher, M.; Casanova, C.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (IOP Publishing, 2014)
      HESS J0632+057 is the only gamma-ray binary known so far whose position in the sky allows observations with ground-based observatories in both the northern and southern hemispheres. Here we report on long-term observations ...
    • Measurement of the EBL spectral energy distribution using the VHE γ-ray spectra of H.E.S.S. blazars 

      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.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M. (EDP Sciences, 2017)
      Very high-energy γ rays (VHE, E ≳ 100 GeV) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. The transparency ...
    • Modelling of the radio emission from the Vela supernova remnant 

      Sushch, I.; Hnatyk, B. (EDP Sciences, 2014)
      Supernova remnants (SNRs) are widely considered to be sites of Galactic cosmic ray (CR) acceleration. Vela is one of the Galactic composite SNRs closest to Earth accompanied by the Vela pulsar and its pulsar wind nebula ...
    • Multiwavelength observations of the binary system PSR B1259−63/LS 2883 around the 2010–2011 periastron passage 

      Chernyakova, M.; Sushch, I.; Abdo, A.A.; Neronov, A.; McSwain, M.V. (Oxford University Press, 2014)
      We report on broad multiwavelength observations of the 2010–2011 periastron passage of the γ -ray loud binary system PSR B1259−63. High-resolution interferometric radio observations establish extended radio emission ...
    • Revisiting the Westerlund 2 field with the HESS telescope array 

      Abramowski, A.; Büsching, I.; Casanova, S.; Davids, I.D.; De Jager, O.C.; Holleran, M.; Sushch, I.; Venter, C. (EDP Sciences, 2011)
      Aims. Previous observations with the HESS telescope array revealed the existence of extended very-high-energy (VHE; E > 100 GeV) γ-ray emission, HESS J1023–575, coincident with the young stellar cluster Westerlund 2. At ...
    • Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT 

      Abramowski, A.; Böttcher, M.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C. (EDP Sciences, 2014)
      Context. Very-high-energy (VHE; E > 100 GeV) γ-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these γ-rays with the extragalactic background light (EBL). ...
    • Search for TeV Gamma-ray emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S. 

      Abramowski, A.; Böttcher, M.; Casanova, C.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2014)
      The long gamma-ray burst (GRB) 100621A, at the time the brightest X-ray transient ever detected by Swift-XRT in the 0:3–10 keV range, has been observed with the H.E.S.S. imaging air Cherenkov telescope array, sensitive ...
    • TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S. 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (Oxford Univ Press, 2014)
      The nonthermal nature of the Xray emission from the shelltype supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both objects. This suggests that ...