Discovery of Non-Thermal X-Rays from the Shell of RCW 86

We report the ASCA (Advanced Satellite for Cosmology and Astrophysics)results of RCW 86, a shell-like supernova remnant (SNR). The bright region inthe X-ray band traces the radio clumpy shell, although details of the structureare different. The X-ray spectrum from each part of the shell can not be fittedto a thin thermal plasma model, but requires, at least three components: a lowtemperature plasma of 0.3 keV, high temperature plasma of > several keV, and apower-law component with a photon index = 3. The abundances of O, Ne, Mg and Siare significantly higher than that of Fe, indicating that RCW 86 is a type IISNR. The absorption column of 3e21 H cm^-2 indicates the distance to the SNR tobe several kpc. The power-law component can be interpreted to be synchrotronradiation of high energy electrons. Assuming energy density equipartitionbetween the magnetic field and the electrons, and using the radio and X-rayspectra, we argue that high energy electrons are accelerated up to 20 TeV. Theacceleration efficiency is, however, different from shell to shell.Comment: 8 pages, 6 figures, accepted for publication in Publi. Astron. Soc. Japan Corrected typo