Fine Structure of the Thermal and Non-thermal X-rays in the Sn 1006 Shell

The North Eastern shell of SN 1006 is the most probable acceleration site of high energy electrons (up to ∼ 100 TeV) with the Fermi acceleration mechanism at the shock front. We resolved non-thermal filaments from thermal emission in the shell with the excellent spatial resolution of Chandra. The non-thermal filaments seem thin sheets with the scales of ∼ 1 arcsec (0.01 pc) and ∼ 20 arcsec (0.19 pc) upstream and downstream of the shock, respectively. In a simple diffusive shock acceleration (DSA) model with the magnetic field parallel to the shock normal, the downstream region should have a highly disordered magnetic field of 30–40 μG. The width at the upstream side is extremely small, comparable to the gyro-radius of the maximum energy electrons. This result might imply that the possible scenario is not the conventional diffusive shock acceleration with a parallel magnetic field but that with a nearly perpendicular field or electron shock surfing acceleration. INTRODUCTION Since the discovery of cosmic rays, the origin and acceleration mechanism up to energies of 1015.5 eV (the “knee” energy) have been long-standing problems. A breakthrough came from the X-ray studies of SN 1006; Koyama et al. (1995) discovered synchrotron X-rays from the shells of this supernova remnant (SNR), indicating the existence of extremely high energy electrons up to TeV energies or more produced by the first order Fermi acceleration. The mechanism for cosmic ray acceleration has also been studied for a long time and the most plausible process is a diffusive shock acceleration (DSA) (e.g. Bell, 1978). Apart from the globally successful picture of DSA, detailed but important processes, such as the injection and the reflection of accelerated particles, are not well understood. The spatial distribution of accelerated particles responsible for the non-thermal X-rays, may provide key information on these unclear processes. Previous observations, however, are too limited in spatial resolution for a detailed study on the structure of shock acceleration process and injection efficiency. Although many observations and theoretical models are made for SN 1006, these problems are still unsolved (e.g. Reynolds, 1998). In this paper, we report on the first results of the spectral and spatial studies of the non-thermal shock structure in the North Eastern (NE) shell of SN 1006 with Chandra. We discuss the spectral analyses and determine the scale lengths of the structures for non-thermal electrons on the basis of a simple and a conventional DSA model. In this paper, we assume the distance of SN 1006 to be 2.18 kpc (Winkler et al. 2003).