Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy
Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy
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使用 Swift-NuSTAR 光谱法展示五个 M31 球状星团源可能的中子星性质
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Will Zhang
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文献类型：
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作者：
T. Maccarone;M. Yukita;A. Hornschemeier;B. Lehmer;V. Antoniou;A. Ptak;D. Wik;A. Zezas;P. Boyd;J. Kennea;K. Page;M. Eracleous;B. Williams;S. Boggs;F. Christensen;W. Craig;C. Hailey;F. Harrison;D. Stern;Will Zhang
我们提出了一个联合Swift-NuSTAR光谱运动的结果M31。我们专注于我们领域中最亮的五个球状星团X射线源。其中两个以前被认为是黑洞候选人的基础上，明显的硬态光谱在光度以上的中子星是在硬态。我们表明，这两个源很可能是Z-源（即低磁场中子星在爱丁顿极限附近吸积），或者可能是明亮的环礁源（低磁场中子星，只是比这个水平稍暗）的基础上，同时斯威夫特和努斯塔光谱，涵盖了更广泛的能量范围。这些新的观测结果揭示了6-8 keV以上的光谱曲率，如果没有努斯塔数据提供的相对于Chandra和XMM-Newton的更广泛的能量覆盖范围，将很难检测到。我们表明，其他三个来源也可能是明亮的中子星星X射线双星，而不是黑洞X射线双星。我们讨论了为什么它应该已经意识到，这是不可能的，这些对象是黑洞的基础上，他们是持久的来源，我们重新审视过去的工作表明，潮汐捕获产品将持续明亮的X射线发射器。我们讨论了这个问题是如何可能是由于忽视磁盘风在旧的工作，预测哪些系统将是持久的，哪些将是瞬态的。
We present the results of a joint Swift-NuSTAR spectroscopy campaign on M31. We focus on the five brightest globular cluster X-ray sources in our fields. Two of these had previously been argued to be black hole candidates on the basis of apparent hard-state spectra at luminosities above those for which neutron stars are in hard states. We show that these two sources are likely to be Z-sources (i.e. low magnetic field neutron stars accreting near their Eddington limits), or perhaps bright atoll sources (low magnetic field neutron stars which are just a bit fainter than this level) on the basis of simultaneous Swift and NuSTAR spectra which cover a broader range of energies. These new observations reveal spectral curvature above 6-8 keV that would be hard to detect without the broader energy coverage the NuSTAR data provide relative to Chandra and XMM-Newton. We show that the other three sources are also likely to be bright neutron star X-ray binaries, rather than black hole X-ray binaries. We discuss why it should already have been realized that it was unlikely that these objects were black holes on the basis of their being persistent sources, and we re-examine past work which suggested that tidal capture products would be persistently bright X-ray emitters. We discuss how this problem is likely due to neglecting disk winds in older work that predict which systems will be persistent and which will be transient.