The X-Ray Structure of the Supernova Remnant 3C 400.2

We present here the results of an X-ray study of the supernova remnant 3C400.2 (G53.6-2.2) using the ASCA data. 3C 400.2 has an unusual morphology atradio wavelengths, suggesting two SNRs superposed along the same line of sight,whereas its X-ray emission is known to be centrally peaked. We investigated theX-ray spectral variation across the remnant using the ASCA GIS and the ROSATPSPC data. The X-ray spectra can be well fitted by thin thermal plasma models.However, there is no significant variation in the temperature and theionization parameter across the remnant. We conclude that it is a single SNRrather than two overlapping SNRs. The centrally peaked X-ray morphology and thethin thermal emission with nearly cosmic abundances indicate that 3C 400.2belongs to a class of ``mixed-morphology SNRs''. We found that the physicalparameters of 3C 400.2 are similar to those of other mixed-morphology SNRs. Themorphology of 3C 400.2 can be explained by a supernova explosion occurring nearto the edge of an interstellar cloud.Comment: 8 pages, 4 figures, to appear in PASJ vol. 5