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arXiv 0710.3682astro-ph
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用XMM-牛顿法探测SNR 1987 A的元素丰度

Probing Elemental Abundances in SNR 1987A Using XMM-Newton

Kevin Heng, Frank Haberl, Bernd Aschenbach, Guenther Hasinger

摘要:

我们报告了XMM-牛顿任务对超新星遗迹(SNR)1987 A的最新观测结果(2007年1月)。自2003年5月Haberl等人(2006年)的观测以来,11条发射线的通量增加了约3至10倍,其中O VIII的775 eV线显示出最大的增加;我们观察到了XMM-牛顿以前未报道的Fe XVII和Fe XVIII的6条线。代表非平衡电离等离子体的两个冲击模型拟合到EPIC-pn谱,产生~ 0.4和~ 3 keV的温度,以及N,O,Ne,Mg,Si,S和Fe的元素丰度。我们证明了N和O的丰度比可以被限制到小于~20%的准确度。在相同的置信区间内,同样的分析表明,C+N+O丰度在~ 1.1 × 10^-4到1.4 × 10^-4之间变化。用Hughes,Hayashi & Koyama(1998)的大麦云云(LMC)值对我们获得的丰度进行归一化,我们发现O、Ne、Mg和Fe丰度不足,而Si和S丰度过高,这与Aschenbach(2007)的发现一致。这样的结果对SNR 1987 A的前身星的单星和双星吸积/合并模型都有影响。在Morris & Podsiadlowski(2006,2007)提出的双星合并假设中,形成赤道内环的物质在合并后被排出,这意味着我们推导出的铁丰度与典型的LMC值不一致,或者在SNR 1987 A的祖星位置铁丰度不足。

英文摘要:

We report on the latest (2007 Jan) observations of supernova remnant (SNR) 1987A from the XMM-Newton mission. Since the 2003 May observations of Haberl et al. (2006), 11 emission lines have experienced increases in flux by factors ~ 3 to 10, with the 775 eV line of O VIII showing the greatest increase; we have observed 6 lines of Fe XVII and Fe XVIII previously unreported by XMM-Newton. A two-shock model representing plasmas in non-equilibrium ionization is fitted to the EPIC-pn spectra, yielding temperatures of ~ 0.4 and ~ 3 keV, as well as elemental abundances for N, O, Ne, Mg, Si, S and Fe. We demonstrate that the abundance ratio of N and O can be constrained to less than ~20% accuracy. Within the same confidence interval, the same analysis suggests that the C+N+O abundance varies from ~ 1.1 to 1.4 X 10^-4. Normalizing our obtained abundances by the Large Magellanic Cloud (LMC) values of Hughes, Hayashi & Koyama (1998), we find that O, Ne, Mg and Fe are under-abundant, while Si and S are over-abundant, consistent with the findings of Aschenbach (2007). Such a result has implications for both the single-star and binary accretion/merger models for the progenitor of SNR 1987A. In the context of the binary merger scenario proposed by Morris & Podsiadlowski (2006, 2007), material forming the inner, equatorial ring was expelled after the merger, implying that either our derived Fe abundance is inconsistent with typical LMC values or that iron is under-abundant at the site of the progenitor star of SNR 1987A.

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