爆发脉冲星GRO J1744-28在第三次再激活期间的同时NuSTAR/Chandra观测
Simultaneous NuSTAR/Chandra observations of the Bursting Pulsar GRO J1744-28 during its third reactivation
摘要：
我们报告了一个10 ks的同时钱德拉/HETG-NuSTAR观测的爆发脉冲星，GRO J1744-28，在其第三次检测到爆发发现以来，经过近18年的平静。源检测到高达60千电子伏的爱丁顿持续通量水平。钱德拉观测到了七次爆发，随后是下降，其中三次也被NuSTAR探测到。定时分析揭示了持续发射脉冲分数与能量（从10%到15%）的略有增加高达10千电子伏，高于此，它保持不变。0.5-70 keV的持续和浸渍发射光谱是相同的误差内，以及描述的黑体（BB），幂律与指数滚降，10 keV的功能，和6.7 keV的发射功能，所有修改中性吸收。假设BB辐射起源于吸积盘，我们估计它的内（磁层）半径约为4 × 10^7 cm，转换为表面偶极场B~ 9 × 10^10 G。钱德拉/HETG光谱解决了6.7千电子伏的功能（准）中性和高度电离的Fe XXV和Fe XXVI发射线。XSTAR模型显示这些线也来自截短的吸积盘。爆发谱的峰值通量比爱丁顿高一个数量级以上，与指数滚降和10 keV特征的幂律拟合良好，与持久谱和倾角谱相比具有相似的拟合值。爆发谱缺乏热分量和任何Fe特征。各向异性（波束）爆发发射可以解释BB和任何Fe成分的缺乏。
英文摘要：
We report on a 10 ks simultaneous Chandra/HETG-NuSTAR observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 years of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5-70 keV spectra of the persistent and dip emission are the same within errors, and well described by a blackbody (BB), a power-law with an exponential rolloff, a 10 keV feature, and a 6.7 keV emission feature, all modified by neutral absorption. Assuming that the BB emission originates in an accretion disc, we estimate its inner (magnetospheric) radius to be about 4x10^7 cm, which translates to a surface dipole field B~9x10^10 G. The Chandra/HETG spectrum resolves the 6.7 keV feature into (quasi-)neutral and highly ionized Fe XXV and Fe XXVI emission lines. XSTAR modeling shows these lines to also emanate from a truncated accretion disk. The burst spectra, with a peak flux more than an order of magnitude higher than Eddington, are well fit with a power-law with an exponential rolloff and a 10~keV feature, with similar fit values compared to the persistent and dip spectra. The burst spectra lack a thermal component and any Fe features. Anisotropic (beamed) burst emission would explain both the lack of the BB and any Fe components.
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