Browsing Faculty of Natural and Agricultural Sciences by Author "1b51c671-239d-44df-8afd-ee35f031bda8"
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The 2014 TeV γ-ray flare of Mrk 501 seen with H.E.S.S.: temporal and spectral constraints on Lorentz invariance violation
Abdalla, H.; Arcaro, C.; Backes, M.; Barnard, M.; Böttcher, M.; Chandra, S.; Krüger, P.P.; Ndiyavala, H.; Seyffert, A.S.; Spanier, F.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M. (IOP Publishing, 2019)The blazar Mrk 501 (z = 0.034) was observed at very-high-energy (VHE, E gsim 100 GeV) gamma-ray wavelengths during a bright flare on the night of 2014 June 23–24 (MJD 56832) with the H.E.S.S. phase-II array of Cherenkov ... -
Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.
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.; H.E.S.S. Collaboration (EDP Sciences, 2018)The diffuse very high-energy (VHE; >100 GeV) γ-ray emission observed in the central 200 pc of the Milky Way by H.E.S.S. was found to follow dense matter distribution in the central molecular zone (CMZ) up to a longitudinal ... -
Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations
Ahnen, M.L.; Munar-Adrover, P.; Abdalla, H.; Barnard, M.; Böttcher, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Richter, S.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Seyffert, A.S.; Spanier, F.; Sushch, I.; H.E.S.S. Collaboration (EDP Sciences, 2018)Context. The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes above the sensitivity ... -
Deeper H.E.S.S. observations of Vela Junior (RX J0852.0-4622): morphology studies and resolved spectroscopy
Abdalla, H.; Barnard, M.; Böttcher, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Richter, S.; Seyffert, A.S.; Sushch, I.; Spanier, F.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; H.E.S.S. Collaboration (EDP Sciences, 2018)Aims. We study γ-ray emission from the shell-type supernova remnant (SNR) RX J0852.0−4622 to better characterize its spectral properties and its distribution over the SNR. Methods. The analysis of an extended High Energy ... -
Detection of variable VHE γ-ray emission from the extra-galactic γ-ray binary LMC P3
Abdalla, H.; Barnard, M.; Böttcher, M.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Ndiyavala, H.; Pekeur, N.W.; Seyffert, A.S.; Spanier, F.; Sushch, I.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; H.E.S.S. Collaboration (EDP Sciences, 2018)Context. Recently, the high-energy (HE, 0.1–100 GeV) γ-ray emission from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered to be modulated with a 10.3-day period, making it the first extra-galactic ... -
Extended VHE γ-ray emission towards SGR1806-20, LBV 1806-20, and stellar cluster Cl 1806-20
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, 2018)Using the High Energy Spectroscopic System (H.E.S.S.) telescopes we have discovered a steady and extended very high-energy (VHE) γ-ray source towards the luminous blue variable candidate LBV 1806−20, massive stellar cluster ... -
First ground-based measurement of sub-20 GeV to 100GeV y-Rays from the Vela pulsar with H.E.S.S. II
Abdalla, H.; Arcaro, C.; Barnard, M.; Böttcher, M.; Chandra, S.; Krüger, P.P.; Ndiyavala, H.; Seyffert, A.S.; Spanier, F.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; H.E.S.S. Collaboration (EDP Sciences, 2018)Aims. We report on the measurement and investigation of pulsed high-energy γ-ray emission from the Vela pulsar, PSR B0833−45, based on observations with the largest telescope of H.E.S.S., CT5, in monoscopic mode, and on ... -
H.E.S.S. discovery of very high energy γ-ray emission from PKS 0625−354
Abdalla, H.; Barnard, M.; Davids, I.D.; Garrigoux, T.; Ivascenko, A.; 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 (Oxford Univ Press, 2018)PKS 0625−354 (z = 0.055) was observed with the four High Energy Stereoscopic System (H.E.S.S.) telescopes in 2012 during 5.5 h. The source was detected above an energy threshold of 200 GeV at a significance level of 6.1σ. ... -
The H.E.S.S. Galactic plane survey
Abdalla, H.; Barnard, M.; Böttcher, M.; 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.; Zacharias, M.; H.E.S.S. Collaboration (EDP Sciences, 2018)We present the results of the most comprehensive survey of the Galactic plane in very high-energy (VHE) γ-rays, including a public release of Galactic sky maps, a catalog of VHE sources, and the discovery of 16 new sources ... -
H.E.S.S. observations of RX J1713.7−3946 with improved angular and spectral resolution: evidence for gamma-ray emission extending beyond the X-ray emitting shell
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, 2018)Supernova remnants exhibit shock fronts (shells) that can accelerate charged particles up to very high energies. In the past decade, measurements of a handful of shell-type supernova remnants in very high-energy gamma ... -
HESS J1741-302: a hidden accelerator in the Galactic plane
Abdalla, H.; Barnard, M.; Böttcher, M.; 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.; Zacharias, M.; H.E.S.S. Collaboration (EDP Sciences, 2018)The H.E.S.S. Collaboration has discovered a new very high energy (VHE, E > 0.1 TeV) γ-ray source, HESS J1741−302, located in the Galactic plane. Despite several attempts to constrain its nature, no plausible counterpart ... -
Multi-messenger observations of a binary neutron star merger
Abdalla, H.; Böttcher, M.; Barnard, M.; H.E.S.S. Collaboration (IOP Publishing, 2017)On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi ... -
A polarized fast radio burst at low Galactic latitude
Petroff, E.; 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 (Oxford Univ Press, 2017)We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 ± 0.8 pc cm−3, a ... -
The population of TeV pulsar wind nebulae in the H.E.S.S. Galactic Plane Survey
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, 2018)The nine-year H.E.S.S. Galactic Plane Survey (HGPS) has yielded the most uniform observation scan of the inner Milky Way in the TeV gamma-ray band to date. The sky maps and source catalogue of the HGPS allow for a systematic ... -
Population study of Galactic supernova remnants at very high γ-ray energies with H.E.S.S.
Abdalla, H.; Barnard, M.; Böttcher, M.; 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.; Zacharias, M.; H.E.S.S. Collaboration (EDP Sciences, 2018)Shell-type supernova remnants (SNRs) are considered prime candidates for the acceleration of Galactic cosmic rays (CRs) up to the knee of the CR spectrum at E ≈ 3 × 1015 eV. Our Milky Way galaxy hosts more than 350 SNRs ... -
A search for new supernova remnant shells in the Galactic plane with H.E.S.S.
Abdalla, H.; Barnard, M.; Böttcher, M.; 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.; Davids, I.D.; H.E.S.S. Collaboration (EDP Sciences, 2018)A search for new supernova remnants (SNRs) has been conducted using TeV γ-ray data from the H.E.S.S. Galactic plane survey. As an identification criterion, shell morphologies that are characteristic for known resolved TeV ... -
A search for very high-energy flares from the microquasars GRS 1915+105, Circinus X-1, and V4641 Sgr using contemporaneous H.E.S.S. and RXTE observations
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, 2018)Context. Microquasars are potential γ-ray emitters. Indications of transient episodes of γ-ray emission were recently reported in at least two systems: Cyg X-1 and Cyg X-3. The identification of additional γ-ray-emitting ... -
Search for γ-ray line signals from dark matter annihilations in the inner galactic halo from 10 years of observations with H.E.S.S.
Abdalla, H.; Barnard, M.; Böttcher, M.; Garrigoux, T.; Ivascenko, A.; Krüger, P.P.; Ndiyavala, H.; Pekeur, N.W.; Seyffert, A.S.; Spanier, F.; Sushch, I.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; H.E.S.S. Collaboration (APS, 2018)Spectral lines are among the most powerful signatures for dark matter (DM) annihilation searches in very-high-energy γ rays. The central region of the Milky Way halo is one of the most promising targets given its large ... -
Searches for gamma-ray lines and 'pure WIMP' spectra from Dark Matter annihilations in dwarf galaxies with H.E.S.S.
Abdalla, H.; Arcaro, C.; Barnard, M.; Böttcher, M.; Chandra, S.; Krüger, P.P.; Ndiyavala, H.; Seyffert, A.S.; Spanier, F.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; H.E.S.S. Collaboration (IOP Publishing, 2018)Dwarf spheroidal galaxies are among the most promising targets for detecting signals of Dark Matter (DM) annihilations. The H.E.S.S. experiment has observed five of these systems for a total of about 130 hours. The data ... -
Searches for gamma-ray lines and 'pure WIMP' spectra from Dark Matter annihilations in dwarf galaxies with H.E.S.S.
Abdalla, H.; Arcaro, C.; Barnard, M.; Böttcher, M.; Chandra, S.; Krüger, P.P.; Ndiyavala, H.; Seyffert, A.S.; Spanier, F.; Van der Walt, D.J.; Van Rensburg, C.; Venter, C.; Wadiasingh, Z.; Zacharias, M.; H.E.S.S. Collaboration (IOP Publishing, 2018)Dwarf spheroidal galaxies are among the most promising targets for detecting signals of Dark Matter (DM) annihilations. The H.E.S.S. experiment has observed five of these systems for a total of about 130 hours. The data ...