Chandra X-ray spectroscopy of a clear dip in GX 13+1
Chandra X-ray spectroscopy of a clear dip in GX 13+1
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GX 13 1 中清晰倾角的钱德拉 X 射线光谱
DOI：
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发表时间：
2014
期刊：
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通讯作者：
N. Robba
中科院分区：
文献类型：
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作者：
A. D’Aì;R. Iaria;T. Salvo;A. Riggio;L. Burderi;N. Robba
语境。源 GX 13+1 是一颗持久、明亮的银河 X 射线双星，拥有一颗吸积中子星。它表现出高度电离的吸收特征，蓝移约为 400 km s -1 ，流出质量速率与吸积速率相似。许多其他 X 射线源表现出热吸收特征，并且它们都同时表现出周期性下降行为。最近，使用长期 X 射线折叠光曲线还确定了 GX 13+1 的倾角周期性，从而在钱德拉档案观测中清楚地识别了此类周期性倾角之一。目标。我们给出了 GX 13+1 周期性倾角的第一个光谱特征，该特征是在 2010 年进行的钱德拉档案观测中发现的。方法。我们使用 Chandra/HETGS 数据（1.0–10 keV 波段）和同期 RXTE/PCA 数据（3.5–25 keV）来分析宽带 X 射线谱。我们采用不同的光谱模型来描述连续发射，并使用 XSTAR 衍生的热吸收体组件来约束高度电离的吸收特征。结果。 1.0−25 keV 连续谱发射与软吸积盘发射模型和光学厚、硬的康普顿化组件一致。持续约 450 秒的倾角事件随着中性吸收体柱密度的增加而得到光谱解析，而我们没有发现热吸收体的柱密度和电离参数相对于倾角外光谱的显着变化。结论。我们认为，相对于同类其他源而言，非常低的倾斜占空比可归因于其长轨道周期和与外盘半径尺寸相比相对较小的大部分中性凸起。
Context. The source GX 13+1 is a persistent, bright Galactic X-ray binary hosting an accreting neutron star. It shows highly ionized absorption features, with a blueshift of ∼400 km s −1 and an outflow-mass rate similar to the accretion rate. Many other X-ray sources exhibit warm absorption features, and they all show periodic dipping behavior at the same time. Recently, a dipping periodicity has also been determined for GX 13+1 using long-term X-ray folded light-curves, leading to a clear identification of one of such periodic dips in an archival Chandra observation. Aims. We give the first spectral characterization of the periodic dip of GX 13+1 found in this archival Chandra observation performed in 2010. Methods. We used Chandra/HETGS data (1.0–10 keV band) and contemporaneous RXTE/PCA data (3.5–25 keV) to analyze the broad-band X-ray spectrum. We adopted different spectral models to describe the continuum emission and used the XSTAR-derived warm absorber component to constrain the highly ionized absorption features. Results. The 1.0−25 keV continuum emission is consistent with a model of soft accretion-disk emission and an optically thick, harder Comptonized component. The dip event, lasting ∼450 s, is spectrally resolved with an increase in the column density of the neutral absorber, while we do not find significant variations in the column density and ionization parameter of the warm absorber with respect to the out-of-dip spectrum. Conclusions. We argue that the very low dipping duty-cycle with respect to other sources of the same class can be ascribed to its long orbital period and the mostly neutral bulge that is relatively small compared with the dimensions of the outer disk radius.