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Session 40 - Supernova Remnants & SN 1987A.
Display session, Thursday, January 08
Exhibit Hall,
Recent discoveries using ASCA and RXTE have demonstrated that hard, nonthermal tails are not uncommon in the X-ray spectra of the shells of young supernova remnants. These tails are interpreted as synchroton radiation from electrons accelerated to TeV energies within the SNR shocks. As such, they provide strong evidence of acceleration of high energy cosmic rays within SNR shocks. The young, X-ray luminous remnants in the Large Magellanic Cloud allow for the study of a full population of SNR's without the biases introduced within the Galaxy by distance and column density. We have systematically searched the ASCA spectra of all the luminous LMC remnants for evidence of hard tails. We find in general that remnants with small diameters have hard components and those with large diameters do not. This suggests that whatever the mechanism producing the tails, it is restricted to the younger remnants. While the presence of an Fe K line at 6.7 keV demonstrates that the hard X-ray emission in some remnants is at least partly thermal, in other remnants no Fe K line is present, suggesting that the tail is predominantly nonthermal. The spectral index of a power law fit to these tails is approximately 3, consistent with that of the nonthermal tails in SN1006 and Cas A. If the hard X-ray emission in the LMC remnants arises from the same mechanism operating in the young Galactic remnants, then it provides the first evidence of high energy cosmic ray production in SNR's outside the Milky Way, and allows an opportunity to track the evolution of the cosmic ray production process.
