Browsing Faculty of Natural and Agricultural Sciences by Author "Aharonian, F."

Now showing items 1-20 of 32

    • Constraints on the multi-TeV particle population in the Coma galaxy cluster with HESS observations 

      Aharonian, F.; Büsching, I.; Davids, I.D.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2009)
      Aims. Galaxy clusters are key targets in the search for ultra high energy particle accelerators. The Coma cluster represents one of the best candidates for such a search owing to its high mass, proximity, and the established ...

    • Detection of very high energy radiation from HESS J1908+063 confirms the Milagro unidentified source MGRO J1908+06 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2009)
      Aims. Detection of a $\gamma$-ray source above 300 GeV is reported, confirming the unidentified source MGRO J1908+06, discovered by the Milagro collaboration at a median energy of 20 TeV. Methods. The source was observed ...

    • Discovery of a VHE gamma-ray source coincident with the supernova remnant CTB 37A 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      Aims. The supernova remnant (SNR) complex CTB 37 is an interesting candidate for observations with very high energy (VHE) γ-ray telescopes such as HESS. In this region, three SNRs are seen. One of them is potentially ...

    • Discovery of gamma-ray emission from the shell-type supernova remnant RCW 86 with HESS 

      Aharonian, F.; Busching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (IOP Publishing, 2009)
      The shell-type supernova remnant (SNR) RCW 86, possibly associated with the historical supernova SN 185, with its relatively large size (about 40' in diameter) and the presence of nonthermal X-rays is a promising target ...

    • Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W 28 (G6.4-0.1) field 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      Aims. Observations of shell-type supernova remnants (SNRs) in the GeV to multi-TeV γ-ray band, coupled with those at millimetre radio wavelengths, are motivated by the search for cosmic-ray accelerators in our Galaxy. The ...

    • Discovery of very high energy y-ray emission from Centaurus A with HESS. 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (IOP Publishing, 2009)
      We report the discovery of faint very high energy (VHE; E > 100 GeV) γ-ray emission from the radio galaxy Centaurus A in observations performed with the High Energy Stereoscopic System (H.E.S.S.) experiment, an imaging ...

    • Discovery of very-high-energy gamma-ray emission from the vicinity of PSR J1913+1011 with HESS 

      Aharonian, F.; Büsching, I.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      The HESS experiment, an array of four Imaging Atmospheric Cherenkov Telescopes with high sensitivity and large field-of-view, has been used to search for emitters of very-high-energy (VHE, >100 GeV) $\gamma$-rays along the ...

    • Discovery of VHE gamma-rays from the high-frequency-peaked BL Lacertae object RGB J0152+017 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      Aims. The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very high-energy (VHE; >100 GeV) $\gamma$-ray source, due to its high X-ray and radio fluxes. Our aim is to understand the radiative processes by ...

    • Discovery of VHE y-rays from the BL Lacertae object PKS 0548-322 

      Aharonian, F.; Büsching, I.; Davids, I.D.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2010)
      Aims. PKS 0548-322 (z=0.069) is a "high-frequency-peaked'' BL Lac object and a candidate very high energy (VHE, E >100 GeV) $\gamma$-ray emitter, due to its high X-ray and radio flux. Observations at the VHE band provide ...

    • Energy spectrum of cosmic-ray electrons at TeV energies 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (APS, 2008)
      The very large collection area of ground-based γ-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600  GeV) cosmic-ray electrons. Here we ...

    • Erratum to "Observations of the sagittarius dwarf galaxy by HESS experiment and search for a dark matter signal" [Astroparticle physics, 29(1) (2008) 55–62] 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C. (Elsevier, 2010)

    • Exploring a SNR/molecular cloud association within HESS J1745-303 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      Aims. HESS J1745−303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength ...

    • HESS observations and VLT spectroscopy of PG 1553+113 

      Aharonian, F.; Büshing, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2008)
      Aims.The properties of the very high energy (VHE; GeV) γ-ray emission from the high-frequency peaked BL Lac PG 1553+113 are investigated. An attempt is made to measure the currently unknown redshift of this object. Methods.VHE ...

    • HESS observations of the prompt and afterglow phases of GRB 060602B 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (IOP Publishing, 2009)
      We report on the first completely simultaneous observation of a gamma-ray burst (GRB) using an array of Imaging Atmospheric Cherenkov Telescopes, which is sensitive to photons in the very high energy (VHE) γ-ray range (gsim ...

    • HESS observations of y-ray bursts in 2003-2007 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2009)
      Aims. Very-high-energy (VHE; $\ga$100 GeV) $\gamma $-rays are expected from $\gamma $-ray bursts (GRBs) in some scenarios. Exploring this photon energy regime is necessary for understanding the energetics and properties ...

    • HESS upper limit on the very high energy gammay-ray emission from the globular cluster 47 Tucanae (Research Note) 

      Aharonian, F.; Busching, I.; Davids, I.D.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP sciences, 2009)
      Observations of the globular cluster 47 Tucanae (NGC 104), which contains at least 23 ms pulsars, were performed with the HESS telescope system. The observations lead to an upper limit of F(E > 800 GeV) < 6.7 × 10−13 cm−2 ...

    • HESS upper limit on the very high energy γ-ray emission from the globular cluster 47 Tucanae 

      Aharonian, F.; Holleran, M.; Büsching, I.; Davids, I.D.; De Jager, O.C.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP Sciences, 2009)
      Observations of the globular cluster 47 Tucanae (NGC 104), which contains at least 23 ms pulsars, were performed with the HESS telescope system. The observations lead to an upper limit of F(E > 800 GeV) < 6.7 × 10−13 cm−2 ...

    • HESS upper limits for Kepler's supernova remnant 

      Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP sciences, 2008)
      Aims. Observations of Kepler's supernova remnant (G4.5+6.8) with the HESS telescope array in 2004 and 2005 with a total live time of 13 h are presented. Methods. Stereoscopic imaging of Cherenkov radiation from extensive ...

    • HESS very-high-energy gamma-ray sources without identified counterparts 

      Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP sciences, 2008)
      Context.The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV–100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this ...

    • Limits on energy dependence of the speed of light from a flare of the active galaxy PKS 2155-304 

      Aharonian, F.; Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (American Physical Society, 2008)
      In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to ...