| Popis: |
The most promising candidate producing cosmic rays with energies below the knee energy (10^{15.5} eV) is the shock wave of supernova remnants (SNRs), the aftermaths of supernova explosions of(massive) stars. However, the acceleration efficiency and the maximum energy of accelerated particles at shock waves still remains a mystery. In particular, it is not known whether the acceleration efficiency perpendicular or parallel to the magnetic field. Therefore, It is essential to perform detailed analyses of the SNR shock waves. RX J0852.0-4622 is a shell-structured SNR with an age of less than 5000 years at a distance of ~1 kpc. In addition, it is one of synchrotron-dominated, bilaterally symmetric SNRs (BSNRs), with the enhanced emission at northwest and southeast regions. Other BSNRs include SN 1006 and G1.9+0.3. The cutoffenergies in the energy spectra of SN 1006 and G1.9+0.3 are found to show an azimuthal dependence, where the cutoffenergy peaks at symmetry axes, suggesting a dependence of the acceleration efficiency on the angle between the shock normal (defined as the direction of the shock wave) and the magnetic field (i.e.,g shock obliquity). In RX J0852.0-4622, the hard X-ray spectral shape of the northwestern rim has been analyzed by the Suzaku HXD, but the spatial distribution of the entire rim has not yet been investigated. In order to reveal spatial variations of the cutoffenergy in RX J0852.0-4622, we analyzed full-rim observations obtained with the Suzaku XIS, which is sensitive in 0.2-10 keV. We performed spatially resolved spectral analysis for the entire rim. By applying the synchrotron loss limit model (Zirakashvili & Aharonian 2007), we measured cutoffenergies at many segmented regions. The cutoffenergy was found to vary from 0.19 keV and 0.64 keV, with a trend of increased values of 0.33 keV and 0.64 keV at the northwest and southeast parts, respectively. This trend (i.e., cutoffenergies are enhanced at symmetry axis) is similar to SN 1006 and G1.9+0.3. Given that the symmetry axis runs parallel to the Galactic plane, the Galactic magnetic field likely penetrates the symmetry axis, suggesting that the acceleration efficiency becomes larger when the shock normal is perpendicular to the magnetic field. In this presentation, we will report the detailed analysis method and results, and discuss the cause of the spatial variation of the cutoffenergy. |
