Abundance Inhomogeneity in the Northeastern Rim of the Cygnus Loop Revealed by Suzaku Observatory

TL;DR

This study uses Suzaku observations to analyze the plasma in the northeastern rim of the Cygnus Loop, revealing inhomogeneous metal abundances and confirming non-ionization equilibrium conditions.

Contribution

It provides the first detailed spatially resolved spectral analysis of this region, highlighting abundance inhomogeneities and their potential origins.

Findings

Abundance inhomogeneities are observed across the field.

Region A shows enhanced absolute abundances compared to other regions.

Relative abundances of Mg/O and Fe/O vary significantly across regions.

Abstract

We present the results of a spatially resolved spectral analysis from four Suzaku observations covering the northeastern rim of the Cygnus Loop. A two-kT_e non-ionization equilibrium (NEI) model fairly well represents our data, which confirms the NEI condition of the plasma there. The metal abundances are depleted relative to the solar values almost everywhere in our field of view. We find abundance inhomogeneities across the field: the northernmost region (Region A) has enhanced absolute abundances compared with other regions. In addition, the relative abundances of Mg/O and Fe/O in Region A are lower than the solar values, while those in the other regions are twice higher than the solar values. As far as we are concerned, neither a circumstellar medium, fragments of ejecta, nor abundance inhomogeneities of the local interstellar medium around the Cygnus Loop can explain the relatively enhanced abundance in Region A. This point is left as an open question for future work.