天鹅座环东北缘至西南缘的等离子体结构
The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim
摘要：
用XMM-Newton从东北到西南观测天鹅座圈。我们把观测区分成南北两条路径，研究了两条路径上的X射线谱。光谱可以很好地拟合由一个组件的非平衡电离（NEI）模型或由两个组件NEI模型。边缘区可以很好地用一个单分量模型来拟合，该模型具有相对较低的\kTe，其金属丰度为亚太阳（0.1- 0.2）。路径的主要部分需要两个组件模型。由于投影效应，我们得出结论，低kTe（约0.2 keV）的组件包围高kTe（约0.6 keV）的组件，后者具有相对较高的金属丰度（约5倍太阳）。由于天鹅座环被认为起源于空腔爆炸，低kTe成分起源于空腔壁，而高kTe成分起源于喷出物。空洞壁分量的通量沿我们的路径显示出很大的变化。我们发现它在西南部地区非常薄，这表明沿着我们的视线有一个井喷。喷出物内的金属分布显示出不均匀性，这取决于元素。O、Ne和Mg在外部区域相对更丰富，而Si、S和Fe集中在内部区域，所有金属都表现出很强的不对称性。这一观测证据暗示了这颗恒星的不对称爆炸。喷出物的丰度也表明，祖星约为15 M太阳。
英文摘要：
The Cygnus Loop was observed from the northeast to the southwest with XMM-Newton. We divided the observed region into two parts, the north path and the south path, and studied the X-ray spectra along two paths. The spectra can be well fitted either by a one-component non-equilibrium 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 sub-solar (0.1--0.2). The major part of the paths requires a two-component model. Due to projection effects, we concluded that the low kTe (about 0.2 keV) component surrounds the high kTe (about 0.6 keV) component, with the latter having relatively high metal abundances (about 5 times solar). Since the Cygnus Loop is thought to originate in a cavity explosion, the low-kTe component 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 path. We found it to be very thin in the south-west region, suggesting a blowout along our line of sight. The metal distribution inside the ejecta shows non-uniformity, 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 the progenitor star to be about 15 M_sun.
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