The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim
The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim
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DOI：
10.1086/523263
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
H. Tsunemi;S. Katsuda;N. Nemes;E. Miller
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文献类型：
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作者：
H. Tsunemi;S. Katsuda;N. Nemes;E. Miller
天鹅座环是用XMM-牛顿从东北向西南观测到的。我们将观测区域分为南北两条路径，并研究了沿这两条路径的X射线光谱。光谱可以用单组分非平衡电离(NEI)模型或双组分非平衡电离(NEI)模型很好地拟合。金属丰度在太阳以下(0.1Z-0.2Z☉)的单组分模型可以很好地拟合边缘区域。路径的主要部分需要两个组件的模型。由于投影效应，我们得出结论：低KTe(~0.2keV)组分围绕着高KTe(~0.6keV)组分，后者具有相对较高的金属丰度(~5倍太阳)。由于天鹅座环被认为起源于空腔爆炸，因此低KTE分量来自空腔壁，而高KTE分量来自喷出物。腔壁组件的通量沿我们的路径显示出很大的变化。我们发现它在西南地区非常薄，这表明沿着我们的视线有一次井喷。喷出物内部金属分布不均匀，取决于元素的不同：O、Ne和Mg在外层相对较丰富，而Si、S和Fe则集中在内层，所有金属都表现出强烈的不对称性。这一观测证据表明，前身恒星发生了不对称的爆炸。喷出物的丰度还表明，其前身质量约为15M☉。
The Cygnus Loop was observed from the northeast to the southwest with XMM-Newton. We divided the observed region into two parts, the north and the south path, and studied the X-ray spectra along the two. The spectra can be well fitted either by a one-component nonequilibrium ionization (NEI) model or by a two-component NEI model. The rim regions can be well fitted by a one-component model with relatively low kTe whose metal abundances are subsolar (0.1-0.2 Z☉). The major part of the paths requires a two-component model. Because of projection effects, we conclude that the low-kTe (~0.2 keV) component surrounds the high-kTe (~0.6 keV) component, with the latter having relatively high metal abundances (~5 times solar). Since the Cygnus Loop is thought to have originated in a cavity explosion, the low-kTe component thus originates from the cavity wall, while the high-kTe component originates from the ejecta. The flux of the cavity-wall component shows a large variation along our paths. We find it to be very thin in the southwest region, suggesting a blowout along our line of sight. The metal distribution inside the ejecta exhibits nonuniformity, depending on the element: O, Ne, and Mg are relatively more abundant in the outer region, while Si, S, and Fe are concentrated in the inner region, with all metals showing strong asymmetry. This observational evidence implies an asymmetric explosion of the progenitor star. The abundance of the ejecta also indicates that the progenitor mass was about 15 M☉.