Recent Submissions

  • Hadronic models of blazars require a change of the accretion paradigm 

    Zdziarski, Andrzej A.; Böttcher, Markus (Oxford University Press, 2015)
    We study hadronic models of broad-band emission of jets in radio-loud active galactic nuclei, and their implications for the accretion in those sources. We show that the models that account for broad-band spectra of blazars ...
  • KAT-7 detection of radio halo emission in the Triangulum Australis galaxy cluster 

    Scaife, Anna M.M.; Oozeer, Nadeem; De Gasperin, Francesco; Brüggen, Marcus; Tasse, Cyril (Oxford University Press, 2015)
    We report the presence of high significance diffuse radio emission from the Triangulum Australis cluster using observations made with the KAT-7 telescope and propose that this emission is a giant radio halo. We compare the ...
  • Early science with the Karoo Array Telescope: a mini-halo candidate in galaxy cluster Abell 3667 

    Riseley, C.J.; Oozeer, N.; Scaife, A.M.M.; Magnus, L.; Wise, M.W. (Oxford University Press, 2015)
    Abell 3667 is among the most well-studied galaxy clusters in the Southern hemisphere. It is known to host two giant radio relics and a head–tail radio galaxy as the brightest cluster galaxy. Recent work has suggested the ...
  • New periodic 6.7 GHz class II methanol maser associated with G358.460−0.391 

    Maswanganye, J.P.; Goedhart, S.; Van der Walt, D.J.; Booth, R.S.; Gaylard, M.J. (Oxford University Press, 2015)
    Eight new class II methanol masers selected from the 6.7 GHz Methanol Multibeam survey catalogues I and II were monitored at 6.7 GHz with the 26 m Hartebeesthoek Radio Astronomy Observatory radio telescope for three years ...
  • Bayesian inference for radio observations 

    Lochner, Michelle; Oozeer, Nadeem; Natarajan, Iniyan; Zwart, Jonathan T.L.; Smirnov, Oleg; Bassett, Bruce A. (Oxford University Press, 2015)
    New telescopes like the Square Kilometre Array (SKA) will push into a new sensitivity regime and expose systematics, such as direction-dependent effects, that could previously be ignored. Current methods for handling such ...
  • Nature of intranight optical variability of BL Lacertae 

    Gaur, Haritma; Böttcher, M.; Gupta, Alok C.; Bachev, R.; Strigachev, A. (Oxford University Press, 2015)
    We present the results of extensive multiband intranight optical monitoring of BL Lacertae during 2010–2012. BL Lacertae was very active in this period and showed intense variability in almost all wavelengths. We extensively ...
  • Particle diffusion and localized acceleration in inhomogeneous AGN jets. I. Steady-state spectra 

    Chen, Xuhui; Böttcher, Markus; Pohl, Martin (Oxford University Press, 2015)
    We study the acceleration, transport, and emission of particles in relativistic jets. Localized stochastic particle acceleration, spatial diffusion, and synchrotron as well as synchrotron self-Compton (SSC) emission are ...
  • Discovery of the VHE gamma-ray source HESS J1832−093 in the vicinity of SNR G22.7−0.2 

    Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (Oxford University Press, 2015)
    The region around the supernova remnant (SNR) W41 contains several TeV sources and has prompted the HESS Collaboration to perform deep observations of this field of view. This resulted in the discovery of the new very high ...
  • Cosmic rays in astrospheres 

    Scherer, K.; Van der Schyff, A.; Ferreira, S.E.S.; Strauss, R.D.; Bomans, D.J. (EDP Sciences, 2015)
    Context: Cosmic rays passing through large astrospheres can be efficiently cooled inside these “cavities” in the interstellar medium. Moreover, the energy spectra of these energetic particles are already modulated in front ...
  • Probing cluster environments of blazars through γγ absorption 

    Sushch, Iurii; Böttcher, Markus (EDP Sciences, 2015)
    Most blazars are known to be hosted in giant elliptic galaxies, but their cluster environments have not been thoroughly investigated. Cluster environments may contain radiation fields of low-energy photons created by nearby ...
  • A detailed calculation of neutral hydrogen ionization frequencies used in turbulence transport models in the heliosphere 

    Engelbrecht, N.E.; Strauss, R.D. (EDP Sciences, 2015)
    It is generally accepted that the solar wind is significantly heated beyond ~10 AU by the turbulent decay of pickup ion generated Alfvénic fluctuations. Here, we present a detailed and general calculation of the pickup ion ...
  • H.E.S.S. detection of TeV emission from the interaction region between the supernova remnant G349.7+0.2 and a molecular cloud 

    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, 2015)
    G349.7+0.2 is a young Galactic supernova remnant (SNR) located at the distance of 11.5 kpc and observed across the entire electromagnetic spectrum from radio to high energy (HE; 0.1 GeV <E< 100 GeV) γ-rays. Radio and ...
  • Short timescale photometric and polarimetric behavior of two BL Lacertae type objects 

    Covino, S.; Böttcher, M.; Baglio, M.C.; Foschini, L.; Sandrinelli, A. (EDP Sciences, 2015)
    Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, i.e. synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, ...
  • The high-energy γ-ray emission of AP Librae 

    Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2015)
    The γ-ray spectrum of the low-frequency-peaked BL Lac (LBL) object AP Librae is studied, following the discovery of very-high-energy (VHE; E> 100 GeV) γ-ray emission up to the TeV range by the H.E.S.S. experiment. This ...
  • Probing the gamma-ray emission from HESS J1834–087 using H.E.S.S. and Fermi LAT observations 

    Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M. (EDP Sciences, 2015)
    Aims: Previous observations with the High Energy Stereoscopic System (H.E.S.S.) have revealed an extended very-high-energy (VHE; E> 100 GeV) γ-ray source, HESS J1834−087, coincident with the supernova remnant (SNR) W41. ...
  • H.E.S.S. reveals a lack of TeV emission from the supernova remnant Puppis A 

    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, 2015)
    Context: Puppis A is an interesting ~4 kyr-old supernova remnant (SNR) that shows strong evidence of interaction between the forward shock and a molecular cloud. It has been studied in detail from radio frequencies to ...
  • Synthesis and characterization of sulfonated poly(pphenylenediamine) prepared by different procedures 

    Amer, Ismael; Young, Desmond A.; Vosloo, Hermanus C.M.; Mokrani, Touhami; Jewell, Linda (Elsevier, 2015)
    The sulfonation of poly(p-phenylenediamine) (P(pPD)) polymer was reported and described in this study. The sulfonated P(pPD) polymers (SP(pPD)) with a degree of sulfonation (S/N molar ratio) range of 0.07–0.38 were prepared ...
  • On a data-dependent choice of the tuning parameter appearing in certain goodness-of-fit tests 

    Allison, J.S.; Santana, L. (Taylor & Francis, 2015)
    We propose a data-dependent method for choosing the tuning parameter appearing in many recently developed goodness-of-fit test statistics. The new method, based on the bootstrap, is applicable to a class of distributions ...
  • Measurement and simulation of neutron monitor count rate dependence on surrounding structure 

    Aiemsa-ad, N.; Krüger, H.; Moraal, H.; Ruffolo, D.; Sáis, A. (American Geophysical Union, 2015)
    Neutron monitors are the premier instruments for precise measurements of time variations (e.g., of solar origin) in the galactic cosmic ray (GCR) flux in the range of ∼1–100 GeV. However, it has proven challenging to ...
  • Multiband optical–NIR variability of blazars on diverse time-scales 

    Agarwal, Aditi; Böttcher, M.; Gupta, Alok C.; Bachev, R.; Strigachev, A. (Oxford University Press, 2015)
    To search for optical variability on awide range of time-scales,we have carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been ...

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