论文标题

Chandra高分辨率X射线频谱从SGR A*

The Chandra High Resolution X-ray Spectrum of Quiescent Emission from Sgr A*

论文作者

Corrales, L., Baganoff, F. K., Wang, Q. D., Nowak, M., Neilsen, J., Markoff, S., Haggard, D., Davis, J., Houck, J., Principe, D.

论文摘要

在静止状态下,SGR A*令人惊讶地昏暗,比其环境的预期低100,000倍。这个问题促使许多理论模型来解释辐射效率低下的积聚流(RIAFS)。 Chandra银河中心(GC)X射线远见计划大约获得了Chandra Hetg数据的大约3 ms(一个月),这为检查具有高分辨率光谱的SGR A*的静态X射线发射提供了唯一的机会。这项工作利用自定义的背景区域和过滤器来删除重叠点源,首次查看了SGR A*的HETG光谱。我们使用立方样条对背景数据集进行建模,并在星际灭绝的影响下使用功率定律加上高斯线的简单参数模型拟合未扣除的sgr a* spectra。我们在HEG光谱中检测到强大的6.7 KEV铁发射线,MEG光谱中的3.1 KEV发射线。在所有情况下,线中心体和等效宽度都与低分辨率CCD光谱测得的宽度一致。对未扣除的HEG +/- 1频谱的检查显示了铁线复合物中的精细结构。除了解决He样铁的谐振和禁止线外,还存在明显的发射特征,在较低的能量下具有较高的统计显着性,在〜1 keV等离子体中可能与Sgr a*的Bondi半径相邻的A*1 keV等离子中的Fexx-XXIV离子。通过这项工作,我们将清洁和堆叠的SGR A*和背景HETG Spectra发布给公众作为特殊的旧数据集。

In quiescence, Sgr A* is surprisingly dim, shining 100,000 times less than expected for its environment. This problem has motivated a host of theoretical models to explain radiatively inefficient accretion flows (RIAFs). The Chandra Galactic Center (GC) X-ray Visionary Program obtained approximately 3 Ms (one month) of Chandra HETG data, offering the only opportunity to examine the quiescent X-ray emission of Sgr A* with high resolution spectroscopy. Utilizing custom background regions and filters for removing overlapping point sources, this work provides the first ever look at stacked HETG spectra of Sgr A*. We model the background datasets with a cubic spline and fit the unbinned Sgr A* spectra with a simple parametric model of a power law plus Gaussian lines under the effects of interstellar extinction. We detect a strong 6.7 keV iron emission line in the HEG spectra and a 3.1 keV emission line in the MEG spectra. In all cases, the line centroids and equivalent widths are consistent with those measured from low-resolution CCD spectra. An examination of the unbinned, stacked HEG+/-1 spectrum reveals fine structure in the iron line complex. In addition to resolving the resonant and forbidden lines from He-like iron, there are apparent emission features arising with higher statistical significance at lower energy, potentially associated with FeXX-XXIV ions in a ~1 keV plasma arising near the Bondi radius of Sgr A*. With this work, we release the cleaned and stacked Sgr A* and background HETG spectra to the public as a special legacy dataset.

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