Upper limits to the SN1006 multi-TeV gamma-ray flux from HESS observations

¹ Max-Planck-Institut für Kernphysik, e-mail: [Conor.Masterson;Gavin.Rowell]@mpi-hd.mpg.de
² Yerevan Physics Institute,
³ University of Durham,
⁴ Centre d'Étude Spatiale des Rayonnements,
⁵ Universität Hamburg, Institut für Experimentalphysik,
⁶ Physique Corpusculaire et Cosmologie, IN2P3/CNRS, Collège de France,
⁷ Institut für Physik, Humboldt-Universität zu Berlin,
⁸ LUTH, UMR 8102 du CNRS, Observatoire de Paris,
⁹ Groupe d'Astroparticules de Montpellier,
¹⁰ Laboratoire Leprince-Ringuet, École Polytechnique
¹¹ European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
¹² Dublin Institute for Advanced Studies
¹³ Service d'Astrophysique, DAPNIA/DSM/CEA, CE Saclay,
¹⁴ Landessternwarte, Königstuhl,
¹⁵ Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier,
¹⁶ Unit for Space Physics, North-West University,
¹⁷ Laboratoire de Physique Nucléaire et de Hautes Énergies, IN2P3/CNRS, Universités Paris VI & VII,
¹⁸ Institut für Theoretische Physik, Ruhr-Universität Bochum,
¹⁹ Institute of Particle and Nuclear Physics, Charles University,
²⁰ University of Namibia,

Received: 11 December 2004
Accepted: 4 February 2005

Abstract

Observations of the shell-type supernova remnant SN1006 have been carried out with the HESS system of Cherenkov telescopes during 2003 (18.2 h with two operating telescopes) and 2004 (6.3 h with all four telescopes). No evidence for TeV γ-ray emission from any compact or extended region associated with the remnant is seen and resulting upper limits at the 99.9% confidence level are up to a factor 10 lower than previously-published fluxes from CANGAROO. For SN1006 at its current epoch of evolution we define limits for a number of important global parameters. Upper limits on the γ-ray luminosity (for E = 0.26 to 10 TeV, distance d = 2 kpc) of   10³³ erg s^-1, and the total energy in corresponding accelerated protons,   10⁵⁰ erg are estimated (for proton energies to 60 TeV and assuming the lowest value  cm^-3 of the ambient target density discussed in literature). Extending this estimate to cover the range of proton energies observed in the cosmic ray spectrum up to the knee (we take here 1 GeV to 3 PeV, assuming a differential particle index -2) gives   10⁵⁰ erg. A lower limit on the post-shock magnetic field of G results when considering the synchrotron/inverse-Compton framework for the observed X-ray flux and γ-ray upper limits.