Volume 551, March 2013
|Number of page(s)||6|
|Section||Interstellar and circumstellar matter|
|Published online||06 March 2013|
Nonthermal emission properties of the northwestern rim of supernova remnant RX J0852.0-4622
1 Universiy of Bonn, Physikalisches Institut, Nussallee 12, Bonn 53115, Germany
2 Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
3 Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025, USA
Received: 9 October 2012
Accepted: 22 January 2013
The supernova remnant (SNR) RX J0852.0-4622 (Vela Jr., G266.6-1.2) is one of the most important SNRs for investigating the acceleration of multi-TeV particles and the origin of Galactic cosmic rays because of its strong synchrotron X-ray and TeV γ-ray emission, which show a shell-like morphology similar to each other. Using the XMM-Newton archival data consisting of multiple pointing observations of the northwestern rim of the remnant, we investigate the spatial properties of the nonthermal X-ray emission as a function of distance from an outer shock wave. All X-ray spectra are well reproduced by an absorbed power-law model above 2 keV. It is found that the spectra show gradual softening from a photon index Γ = 2.56 in the rim region to Γ = 2.96 in the interior region. We show that this radial profile can be interpreted as a gradual decrease of the cutoff energy of the electron spectrum due to synchrotron cooling. By using a simple spectral evolution model that includes continuous synchrotron losses, the spectral softening can be reproduced with the magnetic field strength in the post-shock flow to less than several tens of μG. If this is a typical magnetic field in the SNR shell, γ-ray emission would be accounted for by inverse Compton scattering of high-energy electrons that also produce the synchrotron X-ray emission. Future hard X-ray imaging observations with Nustar and ASTRO-H and TeV γ-ray observations with the Cherenkov Telescope Array (CTA) will allow us to explore other possible explanations of the systematic softening of the X-ray spectra.
Key words: radiation mechanisms: non-thermal / ISM: supernova remnants / X-rays: ISM
© ESO, 2013
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