On the Origin of Galactic Cosmic-Ray Electrons

We present the RXTE PCA X-ray spectrum of SN 1006. This data exhibits evidence of highenergy non-thermal X-ray emission. An analysis of the RXTE PCA data and data from the ASCA SIS and ROSAT PSPC detectors suggests that the entire broad-band X-ray spectrum of SN 1006 may be t with a single non-equilibrium ionization thermal component and a nonthermal component described by a broken power law with a low-energy photon spectral index of about 2.1 and a highenergy index of about 3.0. The shape of the non-thermal spectrum and a comparison of lowand high-energy X-ray images of SN 1006 with one another and with a radio image of the remnant suggest that the only plausible description of the non-thermal X-ray emission of SN 1006 is synchrotron radiation from 10-100 TeV electrons. The inferred properties of the cosmic rays in SN 1006 support the idea that Galactic cosmic rays are predominantly accelerated in supernova remnants.