Now showing items 1-20 of 25

    • 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 ...
    • 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.; H.E.S.S. Collaboration (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 ...
    • Constraints on the gamma-ray emission from the cluster-scale AGN outburst in the hydra A galaxy cluster 

      Abramowski, A.; Büsching, I.; Casanova, S.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)
      Context. In some galaxy clusters, powerful active galactic nuclei (AGN) have blown bubbles with cluster scale extent into the ambient medium. The main pressure support of these bubbles is not known to date, but cosmic rays ...
    • Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N 157B with H.E.S.S 

      Abramowski, A.; Casanova, S.; De Jager, O.C.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)
      We present the significant detection of the first extragalactic pulsar wind nebula (PWN) detected in gamma rays, N 157B, located in the large Magellanic Cloud (LMC). Pulsars with high spin-down luminosity are found to power ...
    • Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2013)
      The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9–185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and ...
    • Discovery of TeV y-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2013)
      Very high-energy γ-ray emission from PKS 0447−439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has ...
    • 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 ...
    • Discovery of VHE emission towards the Carina arm region with the H.E.S.S. telescope array: HESS J1018-589 

      Abramowski, A.; Büsching, I.; Casanova, S.; De Jager, O.C.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)
      The Carina arm region, containing the supernova remnant SNR G284.3–1.8, the high-energy (HE; E > 100 MeV) binary 1FGL J1018.6–5856 and the energetic pulsar PSR J1016–5857 and its nebula, has been observed with the H.E.S.S. ...
    • Discovery of VHE y-ray emission and multi-wavelength observations of the BL Lacertae object 1RXS J101015.9-311909 

      Abramowski, A.; Büsching, I.; Casanova, S.; De Jager, O.C.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Science, 2012)
      1RXS J101015.9 − 311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus (called AGN) belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > ...
    • 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.; H.E.S.S. Collaboration (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 ...
    • H.E.S.S. discovery of VHE y-rays from the quasar PKS 1510-089 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2013)
      The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E ≥ 0.1 ...
    • H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2013)
      Aims. We present very high energy (VHE; E > 100 GeV) data from the γ-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H.E.S.S.) ...
    • 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.; H.E.S.S. Collaboration (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.; H.E.S.S. Collaboration (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.; H.E.S.S. Collaboration (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 ...
    • HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae 

      Abramowski, A.; Büsching, I.; Casanova, S.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (Oxford Univ Press, 2012)
      The massive binary system Eta Carinae and the surrounding HII complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E ≥ 100 GeV) γ -ray emission could be expected. This ...
    • Identification of HESS J1303-631 as a pulsar wind nebula through y-ray, x-ray, and radio observations 

      Abramowski, A.; Büsching, I.; Casanova, S.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M. (EDP Science, 2012)
      Aims. The previously unidentified very high-energy (VHE; E > 100 GeV) γ-ray source HESS J1303−631, discovered in 2004, is re-examined including new data from the H.E.S.S. Cherenkov telescope array in order to identify this ...
    • Long-term TeV and X-ray observations of the gamma-ray binary HESS J0632+057 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (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 extragalactic background light imprint on the spectra of the brightest blazars observed with H.E.S.S. 

      Abramowski, A.; Casanova, S.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M. (EDP Sciences, 2013)
      The extragalactic background light (EBL) is the diffuse radiation with the second highest energy density in the Universe after the cosmic microwave background. The aim of this study is the measurement of the imprint of the ...
    • Probing the extent of the non-thermal emission from the Vela X region at TeV energies with H.E.S.S. 

      Abramowski, A.; Casanova, S.; Krüger, P.P.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)
      Context. Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar (PSR B0833-45). Extended ...