629 research outputs found
Long-term lightcurves from combined unified very high energy g-ray data
No full textContext. Very high-energy (VHE, E > 100 GeV)
γ-ray data are a valuable input for multi-wavelength and
multi-messenger (e.g. combination with neutrino data) studies.
Aims. We aim at the conservation and homogenization of historical,
current, and future VHE γ-ray-data on active galactic nuclei (AGN).
Methods. We have collected lightcurve data taken by major VHE
experiments since 1991 and combined them into long-term lightcurves for several AGN, and
now provide our collected datasets for further use. Due to the lack of common data formats
in VHE γ-ray astronomy, we have defined relevant datafields to be stored
in standard data formats. The time variability of the combined VHE lightcurve data was
investigated, and correlation with archival X-ray data collected by
RXTE/ASM tested.
Results. The combination of data on the prominent blazar Mrk 421 from
different experiments yields a lightcurve spanning more than a decade. From this combined
dataset we derive an integral baseline flux from Mrk 421 that must be lower than 33% of
the Crab Nebula flux above 1 TeV. The analysis of the time variability yields log-normal
flux variations in the VHE-data on Mrk 421.
Conclusions. Existing VHE data contain valuable information concerning
the variability of AGN and can be an important ingredient for multi-wavelength or
multi-messenger studies. In the future, upcoming and planned experiments will provide more
data from many transient objects, and the interaction of VHE astronomy with classical
astronomy will intensify. In this context a unified and exchangeable data format will
become increasingly important
HiSCORE: a new detector for astroparticle and particle physics beyond 10 TeV
No full textProceedings of the Third Roma International Conference on Astroparticle Physics (RICAP'11) held in Roma at “Roma Tre” University from May 24 to May 27, 2011 / Antonio Capone, Giulia De Bonis, Mario De Vincenzi and Aldo Morselli (eds.)The new large-area (100 km2) wide-angle (0.9 sr) air Cherenkov detector HiSCORE (Hundred i Square-km Cosmic ORigin Explorer) aims at the exploration of the cosmic ray and γ-ray sky (accelerator sky) in the so far poorly covered energy range from 10 TeV to 1 EeV. The main motivation for observations in this energy regime is to solve the origin of Galactic cosmic rays. Other questions of astroparticle and particle physics can be addressed in this energy regime. Furthermore, new physics questions might arise by opening the last remaining observation window of γ-ray astronomy (TeV/PeV). HiSCORE is based on non-imaging Cherenkov light-front sampling with sensitive large-area detector modules of the order of 0.5 m2. Sampling the lateral photon density and arrival-time distribution allows the reconstruction of the direction, the energy and the type (mainly via the shower depth) of the primary particle. © 2012 Elsevier B.V.M. Tluczykont, D. Horns, D. Hampf, R. Nachtigall, U. Einhaus, M. Kunnas, T. Kneiske, G. P. Rowel
The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes. Part I: layout and components of the system
No full textH.E.S.S. - the high energy stereoscopic system - is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m2 mirror area for each of four telescopes, and photomultiplier cameras with a large field of view (5°) and small pixels (0.16°). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components - dish, mirrors, and Winston cones - as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper. © 2003 Elsevier B.V. All rights reserved.K. Bernlöhr, O. Carrol, R. Cornils, S. Elfahem, P. Espigat, S. Gillessen, G. Heinzelmann, G. Hermann, W. Hofmanna, D. Horns, I. Jung, R. Kankanyan, A. Katona, B. Khelifi, H. Krawczynski, M. Panter, M. Punch, S. Rayner, G. Rowell, M. Tluczykont and R. van Staahttp://www.elsevier.com/wps/find/journaldescription.cws_home/523319/description#descriptio
The ground-based large-area wide-angle gamma-ray and cosmic-ray experiment HiSCORE
No full textThe question of the origin of cosmic rays and other questions of astroparticle and particle physics can be addressed with indirect air-shower observations above 10 TeV primary energy. We propose to explore the cosmic ray and γ-ray sky (accelerator sky) in the energy range from 10 TeV to 1 EeV with the new ground-based large-area wide angle (ΔΩ ∼ 0.85 sterad) air-shower detector HiSCORE (Hundred i Square-km Cosmic ORigin Explorer). The HiSCORE detector is based on non-imaging air-shower Cherenkov light-front sampling using an array of light-collecting stations. A full detector simulation and basic reconstruction algorithms have been used to assess the performance of HiSCORE. First prototype studies for different hardware components of the detector array have been carried out. The resulting sensitivity of HiSCORE to γ-rays will be comparable to CTA at 50 TeV and will extend the sensitive energy range for γ-rays up to the PeV regime. HiSCORE will also be sensitive to charged cosmic rays between 100 TeV and 1 EeV. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.Martin Tluczykont, Daniel Hampf, Dieter Horns, Tanja Kneiske, Robert Eichler, Rayk Nachtigall and Gavin Rowel
The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes. Part II: mirror alignment and point spread function
No full textMirror facets of the high energy stereoscopic system imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the photomultiplier camera, viewed by a CCD camera. The alignment procedure works reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4° from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications. © 2003 Elsevier B.V. All rights reserved.R. Cornils, S. Gillessen, I. Jung, W. Hofmann, M. Beilicke, K. Bernlöhr, O. Carrol, S. Elfahem, G. Heinzelmann, G. Hermann, D. Horns, R. Kankanyan, A. Katona, H. Krawczynskib, M. Panterb, S. Raynerd, G. Rowell, M. Tluczykont and R. van Staahttp://www.elsevier.com/wps/find/journaldescription.cws_home/523319/description#descriptio
Estimation of the TeV gamma-ray duty cycle of Mrk 421 with Milagro
No full textThe blazar Markarian 421 (Mrk 421) is one of the brightest sources in the extragalactic X-ray/TeV sky. It is also one of the fastest varying TeV γ-ray sources, showing flaring activity on time scales as short as tens of minutes. To know the level of activity of this source, Tluczykont et al. (2007) [1] calculated the fraction of time spent by Mrk 421 in flaring states with fluxes above 1 Crab at TeV energies (i.e., TeV - duty cycle). Here we present an alternative approach to calculate the TeV duty cycle of Mrk 421 taking advantage of the continuous monitoring of the source by the Milagro observatory. Milagro was a water Cherenkov detector sensitive at energies between 100 GeV and 100 TeV. We present our estimation of the TeV - duty cycle and study its robustness
The hardware of the HiSCORE gamma-ray and cosmic ray Cherenkov detector
No full textThe HiSCORE (Hundred Square km Cosmic ORigin Explorer) project is a ground-based large-area wideangle air shower detector array that will measure gamma rays and cosmic rays in the energy range of 10 TeV up to 1EeV. Each detector array station consists of four separate light collectors with an 8-inch photomultiplier (PMT) at each end. The first station prototype has already been deployed to Tunka valley. On-site station integration and first measurements have been made. This poster will focus on the hardware aspects and the first light results of the single station. © 2012 American Institute of Physics.M. Kunnas, R. Nachtigall, S. N. Epimakhov, M. Tluczykont, L. A. Kuzmichev, S. F. Berezhnev, N. M. Budnev, M. Baker, A. Chiavassa, O. B. Chvalaev, O. A. Gress, A. N. Dyachok, U. Einhaus, D. Hampf, D. Horns, A. Ivanova, N. I. Karpov, N. N. Kalmykov, E. N. Konstantinov, A. V. Korobchenko, E. E. Korosteleva, V. A. Kozhin, B. K. Lubsandorzhiev, N. B. Lubsandorzhiev, R. R. Mirgazov, A. Pakhorukov, M. I. Panasyuk, L. V. Pankov, V. Poleschuk, E. G. Popova, V. V. Prosin, V. S. Ptuskin, G. P. Rowell, Yu. A. Semeney, B. A. Shaibonov (junior), A. A. Silaev, A. A. Silaev (junior), A. V. Skurikhin, C. Spiering, L. G. Sveshnikova, R. Wischnewski, I. V. Yashin, and A. V. Zagorodniko
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