标题： 天鹅环北部的丰度不均一性 显示英文标题

标题： The Abundance Inhomogeneity in the Northern Rim of the Cygnus Loop

摘要： 我们用\textit{Suzaku}观测站对天鹅环的北部边缘进行了5次指向观测（P21-P25）。 从空间分辨分析来看，所有光谱都可以很好地由非平衡电离等离子体模型的单个组分拟合。 从最佳拟合参数来看，我们发现除了P21和P22最外层边缘的元素丰度外，重元素的丰度显著低于太阳值。 金属丰度减少的起源尚不清楚，尽管在环的许多其他边缘观测中也报告了类似的不足。 为了解释这些边缘区域的丰度减少，我们考虑了几种可能性。 共振线散射和尘埃凝聚效应降低了丰度值。 然而，这些不足以解释所观察到的丰度减少。 我们发现P21和P22最外层边缘的丰度高于其他区域。 从形态学角度来看，认为这种丰度不均匀性是由环的腔壁破裂或变薄引起的，是合理的。 显示英文摘要

摘要： We observed the northern rim of the Cygnus Loop with the \textit{Suzaku} observatory in 5 pointings (P21-P25). From the spatially resolved analysis, all the spectra are well fitted by the single component of the non-equilibrium ionization plasma model. From the best-fit parameters, we found that the abundances of the heavy elements are significantly lower than the solar values except those at the outermost edge in P21 and P22. The origin of the depleted metal abundances is still unclear while such deficiencies have been reported from many other rim observations of the Loop. To explain these depletion at the rim regions, we considered the several possibilities. The effects of the resonance-line-scattering and the grain condensation lower the values of the abundances. However, these are not sufficient to account for the abundance depletion observed. We found that the abundances at the outermost edge in P21 and P22 are higher than those at the other regions. From the morphological point of view, it is reasonable to consider that this abundance inhomogeneity is derived from the breakout or the thinness of the cavity wall of the Loop.