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arXiv 1703.01263astro-ph.HE
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中子星低质量X射线双星中准周期振荡与吸积态之间的联系

Links between quasi-periodic oscillations and accretion states in neutron star low mass X-ray binaries

S. E. Motta, A. Rouco-Escorial, E. Kuulkers, T. Muñoz-Darias, A. Sanna

摘要:

我们分析了Rossi X射线定时探测器(RXTE)从一个明亮的吸积中子星(NS)低质量X射线双星(LMXB)样本中获得的数据。为了研究准周期变率随吸积状态的变化,我们利用积分分数变率作为吸积态的跟踪器,对这些系统的X射线时间序列中的准周期振荡(QPO)进行了系统的搜索.我们发现,最初在80年代为最亮的LMXB确定的三种QPO类型,即所谓的Z源,水平的、正常的和燃烧的分支振荡(分别为HBO、NBO和FBO)也在亮度稍低的NS LMXB中被识别,即所谓的环礁源,在那里我们看到QPO的行为与HBO和FBO一致。我们比较了我们的NS样本与黑洞(BH)LMXB样本的准周期变化特性。我们确认了在Z源中观察到的HBO、NBO和FBO与BH系统中观察到的C型、B型和A型QPO之间的关联,并将比较扩展到Atoll源中观察到的HBO样和FBO样QPO。我们的结论是BH和弱磁化NS LMXBs的变异性表现出很强的相似性,与QPOs只有弱敏感的性质,在这两类系统的中心紧凑的对象。我们发现,kHz QPO和高频QPO之间的历史关联,看到周围的NS和BH,分别是不明显的,当比较类似的吸积状态在两种系统。

英文摘要:

We analysed the Rossi X-ray Timing Explorer (RXTE) data from a sample of bright accreting neutron star (NS) low-mass X-ray binaries (LMXBs). With the aim of studying the quasi-periodic variability as a function of the accretion regime, we carried out a systematic search of the quasi-periodic oscillations (QPOs) in the X-ray time series of these systems, using the integrated fractional variability as a tracker for the accretion states. We found that the three QPO types originally identified in the '80s for the brightest LMXBs, the so-called Z-sources, i.e., horizontal, normal and flaring branch oscillations (HBOs, NBOs and FBOs, respectively), are also identified in the slightly less bright NS LMXBs, the so-called Atoll sources, where we see QPOs with a behaviour consistent with the HBOs and FBOs. We compared the quasi-periodic variability properties of our NS sample with those of a sample of black hole (BH) LMXBs. We confirm the association between HBOs, NBOs and FBOs observed in Z-sources, with the type-C, type-B and type-A QPOs, respectively, observed in BH systems, and we extended the comparison to the HBO-like and FBO-like QPOs seen in Atoll sources. We conclude that the variability properties of BH and weakly-magnetized NS LMXBs show strong similarities, with QPOs only weakly sensitive to the nature of the central compact object in both classes of systems. We find that the historical association between kHz QPOs and high-frequency QPOs, seen around NSs and BHs, respectively, is not obvious when comparing similar accretion states in the two kinds of systems.

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