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S.P. Hendrick (North Carolina State University)
Supernovae are a prime source of energy, heavy elements, and cosmic rays deposited into the interstellar medium of galaxies, and supernova remnants exhibit that energy and material primarily by X-ray emission. The X-rays are produced both from ISM material shock-heated by the blast wave, and from ejecta heated by a reverse shock. The standard picture of supernova remnant evolution is an ejecta dominated phase, when the reverse shock is prominent, that eventually goes into the Sedov phase when the mass swept up is much larger than the ejecta mass. Important questions concern explosion energy, the composition of material, and relative frequencies of core collapse (Type II, Ib/Ic) and thermonuclear (Type Ia) events. I summarize our observations, with Chandra and XMM-Newton, of 6 older SNRs in the Magellanic Clouds. The remnants range in age from 7,000 to 15,000 years and it was a surprise to find that reverse shock-heated ejecta were still prominent in five. Typing the explosion can be done by comparing O/Fe ratios in the spectra. Four of our LMC objects (0548-70.4, 0534-69.9, DEM L238, and DEM L249) show strong Fe L-shell emission that indicates a Type Ia origin. The other two are from core collapse explosions: SMC remnant 0049-73.6 has O-dominated ejecta, and 0453-68.5 has a pulsar wind nebula in its interior. In each case, the explosion energy was less than the expected 1051 ergs possibly indicating that energy is going into cosmic ray production. Analysis included a new NEI model appropriate for heavy element dominated plasmas.
This work was supported by NASA grants SAO G01-2075X, SAO G03-4097X, and NAG5-13641.
The author(s) of this abstract have provided an email address for comments about the abstract: sphendri@unity.ncsu.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.