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S. Safi-Harb, R. Petre, K.A. Arnaud (NASA/GSFC), J. Keohane (N.C.S.S.M), K. Dyer, S. Reynolds (N.C. State University)
3C397 (G41.1-0.3) is one of the brightest radio SNR's, whose classification as a `mixed-morphology' Composite-type SNR is highly uncertain. We present a broadband imaging and spectral study of 3C397 with ROSAT, ASCA, & RXTE. We show that the X-ray emission from the center is dominated by soft emission (E below 4 keV), and that unlike the Plerionic Composites, the hard X-ray emission arises primarily from the shell-like component.
A broadband spectral study of the X-ray emission in the 0.6-15 keV range shows that at least two components are required: a soft component dominated by line emission from heavily enriched material, and a harder component, characterized by a prominent Fe-K emission line. While equilibrium models fail to describe the soft component, non-equilibrium ionization (NEI) models fit the data adequately, implying that 3C397 is a young SNR. The harder component can be fitted with either a thermal model, or a power law plus a Gaussian line to account for the Fe-K emission line. The total observed flux is ~ 2.6 x 10-11 erg cm-2 s-1, which corresponds to an unabsorbed luminosity Lx (1-9 keV) = 4 x 1036 erg s-1, assuming a distance of 10 kpc. The combined ASCA & RXTE PCA data in the 0.6-15 keV range suggest the presence of a weak third component, whose parameters are poorly determined because of the contamination of the RXTE signal with the emission from the Galactic ridge.
We discuss the X-ray spectrum in the light of thermal emission from an ejecta-dominated component, associated with the SN explosion of a massive star. The harder component is consistent with thermal emission from the ISM shock-heated by the blast wave of an ~ 2,000-yr old SN explosion. However, it is possible that part of this emission is non-thermal. We speculate on the possibility that a compact object is hidden in 3C397, and draw similarities to the Composite-type SNR W50 powered by the jet source, SS433.
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