A CHANDRA SURVEY OF FLUORESCENCE Fe LINES IN X-RAY BINARIES AT HIGH RESOLUTION
A CHANDRA SURVEY OF FLUORESCENCE Fe LINES IN X-RAY BINARIES AT HIGH RESOLUTION
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DOI：
10.1088/0004-637x/715/2/947
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发表时间：
2010-04
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通讯作者：
J. Torrejón;J. Torrejón;Norbert S. Schulz;M. A. Nowak;T. Kallman
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作者：
J. Torrejón;J. Torrejón;Norbert S. Schulz;M. A. Nowak;T. Kallman
铁K线荧光在许多X射线双星（XRB）的X射线光谱中是常见的，是研究X射线源周围物质的基本工具。在本文中，我们提出了一个全面的调查41 XRB（10 HMXB和31 LMXB）与钱德拉特别强调的Fe K区和窄Fe Kα线，在最高的分辨率可能。我们发现：（1）Fe的Kα线始终位于λ = 1.9387 ± 0.0016 λ处，与Fe i ~ Fe x相容，没有发现向高电离态的移动，也没有发现高质量X射线双星（HMXB）和低质量X射线双星（LMXB）之间的差别。(2)该谱线非常窄，FWHM为1.5毫微微，通常钱德拉无法分辨，这意味着后处理材料没有高速旋转。(3)所有的HMXB都具有Fe Kα荧光。相比之下，这样的排放是极其罕见的（约10%）LMXB中，只有少数的大量显示铁钾荧光。然而，这些少数的线和边缘属性与它们的高质量表亲非常相似。(4)Fe线发射的缺乏总是伴随着任何可检测的K边缘的缺乏。(5)得到了Fe Kα线等效宽度随后处理材料密度柱增长的经验曲线，EWKα与NH的关系表明，它与致密天体周围球形分布的后处理区是一致的。(6)我们发现，在XRB荧光遵循X射线鲍德温效应，以前只发现在活动星系核的X射线光谱。我们将这一发现解释为中性Fe丰度随着X射线照射的增加而减少的证据，并用它来解释Cyg X-1的一些光谱状态，作为LMXBs中缺乏窄Fe线发射的可能原因。(7)最后，我们研究了与线荧光相关的康普顿肩和非对称线轮廓等异常形态。具体来说，我们提出的第一个康普顿肩的证据在HMXB X1908+075。此外，4U 1700 −37和LMC X-4的Fe Kα线呈现出不对称的翼，表明在这些系统中存在高度结构化的恒星风。
Fe K line fluorescence is commonly observed in the X-ray spectra of many X-ray binaries (XRBs) and represents a fundamental tool to investigate the material surrounding the X-ray source. In this paper, we present a comprehensive survey of 41 XRBs (10 HMXBs and 31 LMXBs) with Chandra with specific emphasis on the Fe K region and the narrow Fe Kα line, at the highest resolution possible. We find that (1) the Fe Kα line is always centered at λ = 1.9387 ± 0.0016 Å, compatible with Fe i up to Fe x; we detect no shifts to higher ionization states nor any difference between high mass X-ray binaries (HMXBs) and low mass X-ray binaries (LMXBs). (2) The line is very narrow, with FWHM ⩽ 5 mÅ, normally not resolved by Chandra which means that the reprocessing material is not rotating at high speeds. (3) Fe Kα fluorescence is present in all the HMXBs in the survey. In contrast, such emissions are astonishingly rare (∼10%) among LMXBs where only a few out of a large number showed Fe K fluorescence. However, the line and edge properties of these few are very similar to their high mass cousins. (4) The lack of Fe line emission is always accompanied by the lack of any detectable K edge. (5) We obtain the empirical curve of growth of the equivalent width of the Fe Kα line versus the density column of the reprocessing material, i.e., EWKα versus NH, and show that it is consistent with a reprocessing region spherically distributed around the compact object. (6) We show that fluorescence in XRBs follows the X-ray Baldwin effect as previously only found in the X-ray spectra of active galactic nuclei. We interpret this finding as evidence of decreasing neutral Fe abundance with increasing X-ray illumination and use it to explain some spectral states of Cyg X-1 as a possible cause of the lack of narrow Fe line emission in LMXBs. (7) Finally, we study anomalous morphologies such as Compton shoulders and asymmetric line profiles associated with the line fluorescence. Specifically, we present the first evidence of a Compton shoulder in the HMXB X1908+075. Also, the Fe Kα lines of 4U1700−37 and LMC X-4 present asymmetric wings, suggesting the presence of highly structured stellar winds in these systems.