Observation of Kes 27: A Typical Mixed-Morphology SNR
  We report here on the observation of Kes 27, a proto-typical mixed-morphology SNR, using ASCA. It clearly shows a filled-center structure in the X-ray region while a shell structure in the radio region. There are two radio bright regions: one is in the center, while the other is in the east rim. The X-ray intensity peak coincides well with the radio bright region at the center. The X-ray spectrum was well-fitted by a collisional ionization equilibrium model with solar abundances. Taking into account the ionization parameter (>10^{12} cm^{-3} s) and the plasma density (0.39 cm^{-3}), we found that the age of the SNR is longer than 8x10^4 yr. The hardness ratio map indicates that the inner region shows a harder spectrum than that in the outer region, which does not come from the heavier interstellar absorption feature, but from the higher temperature. There is a temperature gradient from the innner region (0.84 keV) toward outer region (0.59 keV), indicating that the thermal conduction does not play an important role. 
Hideyuki Enoguchi, Hiroshi Tsunemi, Emi Miyata, and Kumi Yoshita