FREQUENCY VARIATION OF THE KILOHERTZ QUASI-PERIODIC OSCILLATIONS AND THE FLUX OF THE BAND-LIMITED NOISE IN SCORPIUS X-1
FREQUENCY VARIATION OF THE KILOHERTZ QUASI-PERIODIC OSCILLATIONS AND THE FLUX OF THE BAND-LIMITED NOISE IN SCORPIUS X-1
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DOI：
10.1088/0004-637x/690/2/1363
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发表时间：
2008-09
期刊：
影响因子：
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通讯作者：
Xiaofeng Cao;Wenfei Yu
中科院分区：
文献类型：
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作者：
Xiaofeng Cao;Wenfei Yu
利用Rossi X射线定时探测器对最亮的中子星星低质量X射线双星天蝎座X-1的水平分支（HB）和上正常分支（NB）同时观测到的0.5-16 Hz范围内的kHz准周期振荡（QPO）和带限噪声（BLN）进行了研究。我们发现双kHz QPO频率与HB上BLN时间尺度上发生的通量变化正相关，与先前报道的NB上正常分支振荡（NBO）时间尺度上的正相关关系相反，这表明尽管它们沿着色-色轨道顺序发生，但BLN和NBO是不同的起源。我们还提出的证据表明，双kHz QPO之间的频率间隔随着BLN时间尺度上的通量降低2-3 Hz，这与Z源在HB上跟踪的较长时间尺度上的趋势一致。这进一步表明，与BLN相关的流量变化源于盘吸积流中的质量吸积率变化。我们讨论了这些结果对我们理解BLN的影响。
We study the kilohertz quasi-periodic oscillations (kHz QPOs) and the band-limited noise (BLN) in the 0.5–16 Hz range observed simultaneously on the horizontal branch (HB) and on the upper normal branch (NB) of the brightest neutron star low-mass X-ray binary Scorpius X-1 with observations performed with the Rossi X-Ray Timing Explorer. We find that the twin kHz QPO frequencies are positively correlated with the flux variations taking place on the BLN timescales on the HB, in contrast to the anticorrelation held on the timescale of the normal-branch oscillation (NBO) on the NB reported previously, suggesting that although they occur in sequence along the color–color tracks, the BLN and the NBO are of different origin. We also present evidence that the frequency separation between the twin kHz QPOs decreases with the flux by 2–3 Hz on the BLN timescales, which is consistent with the trend on the longer timescale that the Z source traces on the HB. This further suggests that the flux variation associated with the BLN originates from the mass accretion rate variation in the disk accretion flow. We discuss the implications of these results for our understanding of the BLN.