Another Abundance Inhomogeneity in the South East Limb of the Cygnus Loop

Abstract

Abstract We observed the south east (SE) limb of the Cygnus Loop with Suzaku. Our spatially-resolved spectroscopic study shows that a one-$kT_\mathrm{e}$ non-equilibrium ionization model represents our spectra fairly well. We find that the metal abundances obtained are all depleted relative to the solar values with a positional dependence along the radial direction of the Cygnus Loop. The abundances in the very edge of the limb show about half the solar value, whereas other regions inside the Loop show about 0.2-times the solar value, which has been believed to be a typical value for the Cygnus Loop limb. The “enhanced” abundance in the very edge of the SE limb is quite similar to that found in the north-east (NE) limb of the Loop, and thus this is another evidence of an abundance inhomogeneity in the limb regions of the Loop. The radio map shows a quite different feature: the NE limb is in the radio bright region, while the SE limb shows almost no radio. Therefore, the metal abundance variation in the SE limb can not be attributed to non-thermal emission. The abundance inhomogeneity as well as the metal depletion down to 0.2 times the solar value still remain an open question.