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Session 99 - Supernovae & Supernova Remnants.
Oral session, Friday, January 09

[99.04] Nonthermal Emission From SNR G347.5-0.5: Another Case of Cosmic Ray Acceleration?

P. Slane, P. Plucinsky, I. M. Harrus (SAO), J. P. Hughes (Rutgers), A. J. Green, B. M. Gaensler (U.Sydney)

While standard wisdom has long held that a significant component of the cosmic ray spectrum is the result of particle acceleration by shocks in supernova remnants, only recently has compelling evidence of such a process been observed. Studies carried out with the ASCA observatory have clearly established the nonthermal nature of the emission from the limb-brightened regions of SN 1006 (Koyama et al. 1995). Typically, X-ray emission from SNR shells is in the form of thermal X-rays from hot gas. For SN 1006, however, the X-ray emission from the shell is apparently synchrotron radiation from electrons accelerated by the SNR blast wave to energies as high as 100 TeV (Reynolds 1996).

Spectral results similar to those for SN 1006 are observed for the remnant G347.5--0.5, a bright SNR discovered in the ROSAT All-Sky Survey (Pfeffermann amp; Aschenbach 1996). Koyama et al. (1997) serendipitously observed the northwest shell of the remnant in a portion of an ASCA Galactic Plane survey and found that the emission from this region is nonthermal. Here we present results from our pointed ASCA observations of G347.5--0.5. We confirm the nonthermal spectral results for regions along the entire western shell and also find similar nonthermal emission, although with a different spectral index, from the remainder of the SNR. We also observe soft X-ray emission from a central point source in the remnant which appears to be consistent with blackbody radiation from a neutron star. Moreover, we have carried out radio observations with the Molonglo Observatory Synthesis Telescope and observe faint radio emission from narrow regions directly along the bright nonthermal X-ray features from the remnant. We discuss these results in terms of evolutionary scenarios for the remnant and investigate the implications for particle acceleration by the SNR blast wave.

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