Discovery of Tev Gamma Rays from Sn1006: Further Evidence for the Snr Origin of Cosmic Rays

This paper reports the first discovery of TeV gamma-ray emission from a supernova remnant made with the CANGAROO 3.8 m Telescope. TeV gamma rays were detected at the sky position and extension coincident with the north-east (NE) rim of shell-type Supernova remnant (SNR) SN1006 (Type Ia). SN1006 has been a most likely candidate for an extended TeV Gamma-ray source, since the clear synchrotron X-ray emission from the rims was recently observed by ASCA (Koyama et al. 1995), which is a strong evidence of the existence of very high energy electrons up to hundreds of TeV in the SNR. The observed TeV gamma-ray flux was (2.4± 0.5(statistical)± 0.7(systematic))× 10 cm s (≥ 3.0± 0.9 TeV) and (4.6± 0.6± 1.4)× 10 cm s (≥ 1.7± 0.5 TeV) from the 1996 and 1997 observations, respectively. Also we set an upper limit on the TeV gamma-ray emission from the SW rim, estimated to be 1.1× 10 cm s (≥ 1.7± 0.5 TeV, 95% CL) in the 1997 data. The TeV gamma rays can be attributed to the 2.7 K cosmic background photons up-scattered by electrons of energies up to about 10 eV by the inverse Compton (IC) process. The observed flux of the TeV gamma rays, together with that of the non-thermal X-rays, gives firm constraints on the acceleration process in the SNR shell; a magnetic field of 6.5±2 μG is inferred from both the synchrotron X-rays and inverse Compton TeV gamma-rays, which gives entirely consistent mechanisms that electrons of energies up to 10 eV are produced via the shock acceleration in SN1006. Subject headings: gamma rays:observations – ISM:individual (SN1006) – supernova remnant