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          Institute: MPI für Kernphysik     Collection: High-Energy Astrophysics     Display Documents

ID: 51218.0, MPI für Kernphysik / High-Energy Astrophysics
Observations of H1426+428 with HEGRA - Observations in 2002 and reanalysis of 1999&2000 data
Authors:Aharonian, F. A.; Akhperjanian, A. G.; Beilicke, M.; Bernlöhr, K.; Bojahr, H.; Bolz, O.; Borst, H.; Coarasa, T.; Contreras, J. L.; Cortina, J.; Denninghoff, S.; Fonseca, V.; Girma, M.; Gotting, N.; Heinzelmann, G.; Hermann, G.; Heusler, A.; Hofmann, W.; Horns, D.; Jung, I.; Kankanyan, R.; Kestel, M.; Kettler, J.; Kohnle, A.; Konopelko, A.; Kornmeyer, H.; Kranich, D.; Krawczynski, H.; Lampeitl, H.; Lopez, M.; Lorenz, E.; Lucarelli, F.; Mang, O.; Meyer, H.; Mirzoyan, R.; Moralejo, A.; Ona, E.; Panter, M.; Plyasheshnikov, A.; Pühlhofer, G.; Rauterberg, G.; Reyes, R.; Rhode, W.; Ripken, J.; Rohring, A.; Rowell, G. P.; Sahakian, V.; Samorski, M.; Schilling, M.; Siems, M.; Sobzynska, D.; Stamm, W.; Tluczykont, M.; Völk, H. J.; Wiedner, C. A.; Wittek, W.
Date of Publication (YYYY-MM-DD):2003-05
Title of Journal:Astronomy & Astrophysics
Journal Abbrev.:Astron. Astrophys.
Issue / Number:2
Start Page:523
End Page:528
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The HEGRA system of imaging air Cherenkov telescopes has been used to observe the BL Lac object H1426+428 ( z=0.129) for 217.5 hours in 2002. In this data set alone, the source is detected at a confidence level of $5.3~\sigma$, confirming this object as a TeV source. The overall flux level during the observations in 2002 is found to be a factor of $\approx$2.5 lower than during the previous observations by HEGRA in 1999 and 2000. A new spectral analysis has been carried out, improving the signal-to-noise ratio at the expense of a slightly increased systematic uncertainty and reducing the relative energy resolution to $\Delta E/E\le 12\%$ over a wide range of energies. The new method has also been applied to the previously published data set taken in 1999 and 2000, confirming the earlier claim of a flattening of the energy spectrum between 1 and 5 TeV. The data set taken in 2002 shows again a signal at energies above 1 TeV. We combine the energy spectra as determined by the CAT and VERITAS groups with our reanalyzed result of the 1999 and 2000 data set and apply a correction to account for effects of absorption of high energy photons on extragalactic background light in the optical to mid infrared band. The shape of the inferred source spectrum is mostly sensitive to the characteristics of the extragalactic background light between wavelengths of 1 and 15 $\mu$m.
Free Keywords:BL Lacertae objects: individual H1426+428 -- gamma-rays: observations -- intergalactic medium
External Publication Status:published
Document Type:Article
Affiliations:MPI für Kernphysik/Group H. J. Völk/High Energy Astrophysics (F. Aharonian)
MPI für Kernphysik/Group W. Hofmann/Experimental High-Energy Astrophysics (M. Panter, G. Hermann)
External Affiliations:Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany; Univ Complutense, Fac Ciencias Fis, E-28040 Madrid, Spain; Univ Hamburg, Inst Phys Expt, D-22761 Hamburg, Germany; Univ Kiel, Inst Expt & Angew Phys, D-24118 Kiel, Germany; Univ Wuppertal, Fachbereich Phys, D-42097 Wuppertal, Germany; Yerevan Phys Inst, Yerevan 375036, Armenia
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