The northeast 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 nonthermal filaments from thermal emission in the shell with the excellent spatial resolution of Chandra. The thermal component is extended over $100 00 (about 1 pc at 1.8 kpc distance) in width, consistent with the shock width derived from the Sedov solution. The spectrum is fitted with a thin thermal plasma of kT ¼ 0:24 keV in nonequilibrium ionization, typical for a young supernova remnant. The nonthermal filaments are likely thin sheets with scale widths of $4 00 (0.04 pc) and $20 00 (0.2 pc) upstream and downstream, respectively. The spectra of the filaments are fitted with a power-law function of index 2.1-2.3, with no significant variation from position to position. In a standard diffusive shock acceleration model, the extremely small scale length in the upstream region requires the magnetic field nearly perpendicular to the shock normal. The injection efficiency () from thermal to nonthermal electrons around the shock front is estimated to be $1 Â 10 À3 under the assumption that the magnetic field in the upstream region is 10 lG. In the filaments, the energy densities of the magnetic field and nonthermal electrons are similar to each other, and both are slightly smaller than that of thermal electrons. These results suggest that the acceleration occurs in more compact regions with larger efficiency than suggested by previous studies. Subject headings: acceleration of particles -ISM: individual (SN 1006) -shock wavessupernova remnants -X-rays: ISM

No abstract

High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.

Using the Chandra Advanced CCD Imaging Spectrometer Imaging array (ACIS-I), we have carried out a deep hard X-ray observation of the Galactic plane region at (l, b) ≈ (28. • 5, 0. • 0), where no discrete X-ray source had been reported previously. We have detected 274 new point X-ray sources (4 σ confidence) as well as strong Galactic diffuse emission within two partially overlapping ACIS-I fields (∼ 250 arcmin 2 in total). The point source sensitivity was 1 code 662, NASA/GSFC, ∼ 3 × 10 −15 erg s −1 cm −2 in the hard X-ray band (2 -10 keV) and ∼ 2 × 10 −16 erg s −1 cm −2 in the soft band (0.5 -2 keV). Sum of all the detected point source fluxes accounts for only ∼ 10 % of the total X-ray flux in the field of view. Even hypothesizing a new population of much dimmer and numerous Galactic point sources, the total observed X-ray flux cannot be explained. Therefore, we conclude that X-ray emission from the Galactic plane has truly diffuse origin. Removing point sources brighter than ∼ 3 × 10 −15 erg s −1 cm −2 (2-10 keV), we have determined the Galactic diffuse X-ray flux as 6.5 ×10 −11 erg s −1 cm −2 deg −2 (2-10 keV). Only 26 point sources were detected both in the soft and hard bands, indicating that there are two distinct classes of the X-ray sources distinguished by the spectral hardness ratio. Surface number density of the hard sources is only slightly higher than that measured at the high Galactic latitude regions, indicating that majority of the hard sources are background AGNs. Following up the Chandra observation, we have performed a near-infrared (NIR) survey with SOFI at ESO/NTT. Almost all the soft X-ray sources have been identified in NIR and their spectral types are consistent with main-sequence stars, suggesting most of them are nearby X-ray active stars. On the other hand, only 22 % of the hard sources had NIR counterparts, which are presumably Galactic. From X-ray and NIR spectral study, they are most likely to be quiescent cataclysmic variables. Our observation suggests a population of 10 4 cataclysmic variables in the entire Galactic plane fainter than ∼ 2 × 10 33 erg s −1 . We have carried out a precise spectral study of the Galactic diffuse X-ray emission excluding the point sources. Confirming previous results, we have detected prominent emission lines from highly ionized heavy elements in the diffuse emission. In particular, central energy of the iron emission line was determined as 6.52 +0.08 −0.14 keV (90 % confidence), which is significantly lower than what is expected from a plasma in thermal equilibrium. The downward shift of the iron line center energy suggests non-equilibrium ionization states of the plasma, or presence of the non-thermal process to produce 6.4 keV fluorescent lines.

؉ , but the overhang reappeared following concomitant deletion of pku70 ؉ . Our data suggest that the Rad50 complex can process DSB ends and telomere ends in the presence of the Ku heterodimer. However, the Ku heterodimer inhibits processing of DSB ends and telomere ends by alternative nucleases in the absence of the Rad50-Rad32 protein complex. While we have identified Exo1 as the alternative nuclease targeting DNA break sites, the identity of the nuclease acting on the telomere ends remains elusive.