Browsing Faculty of Natural and Agricultural Sciences by Author "Sheidaei, F."
Now showing items 1-15 of 15
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The 2010 very high energy γ-ray flare and 10 years of multi-wavelength observations of M 87
Abramowski, A.; Büsching, I.; De Jager, O.C.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (IOP Publishing, 2012)The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3 – 6) × 109 M☉) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) γ-ray ... -
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 extended VHE Y-ray emission from the vicinity of the young massive stellar cluster Westerlund 1
Abramowski, A.; Büsching, I.; De Jager, O.C.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)Aims. Results obtained in very-high-energy (VHE; E≥100GeV) γ-ray observations performed with the H.E.S.S. telescope array are used to investigate particle acceleration processes in the vicinity of the young massive stellar ... -
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 hard-spectrum y-ray emission from the BL Lacertae object 1ES 0414+009
Abramowski, A.; Büsching, I.; De Jager, O.C.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2012)Context. 1ES 0414 + 009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high-energy (VHE, E > 100 GeV) γ-rays due to its high X-ray and radio flux. Aims. ... -
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 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 > ... -
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 ... -
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 ... -
Search for dark matter annihilation signals from the fornax galaxy cluster with HESS
Abramowski, A.; Büsching, I.; De Jager, O.C.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (IOP Publishing, 2012)The Fornax galaxy cluster was observed with the High Energy Stereoscopic System for a total live time of 14.5 hr, searching for very high energy (VHE; E > 100GeV) γ -rays from dark matter (DM) annihilation. No significant ... -
Search for photon line-like signatures from dark matter annihilations 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 (APS, 2013)Gamma-ray line signatures can be expected in the very-high-energy (VHE; E_\gamma > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable ... -
Spectral analysis and interpretation of the Y-ray emission from the starburst galaxy NGC 253
Abramowski, A.; Büsching, I.; Casanova, S.; Pekeur, N.W.; Sheidaei, F.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (IOP Publishing, 2012)Very high energy (VHE; E ≥ 100 GeV) and high-energy (HE; 100 MeV ≤ E ≤ 100 GeV) data from γ-ray observations performed with the H.E.S.S. telescope array and the Fermi-LAT instrument, respectively, are analyzed in order to ...