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

Observations of the shell-type supernova remnant SN1006 have been carried out with the H.E.S.S. system of Cherenkov telescopes during 2003 (18.2h with two operating telescopes) and 2004 (6.3h 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 previouslypublished fluxes from CANGAROO. For SN1006 at its current epoch of evolution we give 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 Lγ < 1.7 × 10 33 erg s, and the total energy in corresponding accelerated protons, Wp < 1.6 × 10 50 erg (for proton energies Ep ∼ 1.5 to 60 TeV and assuming the lowest value n = 0.05 cm −3 of the ambient target density discussed in literature) are estimated. Extending this estimate to cover the range of proton energies observed in the cosmic ray spectrum up to the knee (we take here Ep ∼ 1 GeV to 3 PeV, assuming a differential particle index −2) gives Wp < 6.3 × 10 50 erg. A lower limit on the post-shock magnetic field of B > 25μG results when considering the synchrotron/inverse-Compton framework for the observed X-ray flux and γ-ray upper limits.