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arXiv 1010.0125astro-ph.HE
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磁化中子星光谱的吸收特征

Absorption Features in Spectra of Magnetized Neutron Stars

V. Suleimanov, V. Hambaryan, A. Y. Potekhin, G. G. Pavlov, M. van Adelsberg, R. Neuhaeuser, K. Werner

摘要:

某些磁化孤立中子星(NS)的X射线谱显示出等效宽度(EW)为50 - 200 eV的吸收特征,其性质尚未完全了解。为了解释强磁化(B ~ 10^{14} G)X射线暗隔离NS(XDINSs)软X射线谱中的显著吸收特征,我们从理论上研究了不同的NS局域表面模型,包括裸露的凝聚铁表面和部分电离的氢模型大气,在凝聚表面上方有半无限薄的大气.我们还开发了一个程序,用于计算NS表面上不同温度和磁场分布的磁化中子星的光变曲线和积分出射谱。我们比较了XDINS RBS 1223的计算和观测的光变曲线和积分光谱的一般性质,并得出结论,观测结果可以用凝聚铁表面上方的薄氢气氛来解释,而XDINS表面上不太可能存在强的环形磁场分量。我们认为,在软X射线光谱的中心紧凑型天体(CCO)1 E 1207.4-5209(以下简称1 E 1207)的谐波间隔吸收功能对应于峰值的能量依赖性的自由-自由不透明度的量子化磁场,称为量子振荡。为了探索这些量子振荡的可观测性质,我们计算了B ~ 10^{10} - 10^{11} G(即,电子回旋能量E_{c,e} ~ 0.1 - 1 keV)和T_eff = 1 - 3 MK。这种情况被认为是1 E 1207的典型情况。我们表明,可观察到的功能,在电子回旋谐波与电子战\approx 100 - 200 eV的,可以出现由于这些量子振荡。

英文摘要:

The X-ray spectra of some magnetized isolated neutron stars (NSs) show absorption features with equivalent widths (EWs) of 50 - 200 eV, whose nature is not yet well known. To explain the prominent absorption features in the soft X-ray spectra of the highly magnetized (B ~ 10^{14} G) X-ray dim isolated NSs (XDINSs), we theoretically investigate different NS local surface models, including naked condensed iron surfaces and partially ionized hydrogen model atmospheres, with semi-infinite and thin atmospheres above the condensed surface. We also developed a code for computing light curves and integral emergent spectra of magnetized neutron stars with various temperature and magnetic field distributions over the NS surface. We compare the general properties of the computed and observed light curves and integral spectra for XDINS RBS\,1223 and conclude that the observations can be explained by a thin hydrogen atmosphere above the condensed iron surface, while the presence of a strong toroidal magnetic field component on the XDINS surface is unlikely. We suggest that the harmonically spaced absorption features in the soft X-ray spectrum of the central compact object (CCO) 1E 1207.4-5209 (hereafter 1E 1207) correspond to peaks in the energy dependence of the free-free opacity in a quantizing magnetic field, known as quantum oscillations. To explore observable properties of these quantum oscillations, we calculate models of hydrogen NS atmospheres with B ~ 10^{10} - 10^{11} G (i.e., electron cyclotron energy E_{c,e} ~ 0.1 - 1 keV) and T_eff = 1 - 3 MK. Such conditions are thought to be typical for 1E 1207. We show that observable features at the electron cyclotron harmonics with EWs \approx 100 - 200 eV can arise due to these quantum oscillations.

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