4U 1636-53的RossiXTE监测：I.长期演化与kHz准周期振荡
RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations
摘要：
我们用Rossi X射线定时探测器（RXTE）对环礁型中子星低质量X射线双星4U 1636-53进行了一年半的观测。我们的活动包括两天间隔的短（~2 ks）点，定期监测源的光谱和定时特性。在活动期间，我们观察到一个明显的长期振荡，周期约为30-40天，已经在RXTE全天监视器的光变曲线中看到，这对应于硬（岛）和软（香蕉）状态之间的定期转换。我们在大约三分之一的观测中检测到kHz QPO，其中大部分处于软（香蕉）状态。被确定为较低的kHz QPO的峰的频率的分布被发现是不同于先前在一个独立的数据集中观察到的。这表明系统中的kHz QPO没有显示出固有的优选频率。
英文摘要：
We have monitored the atoll-type neutron star low-mass X-ray binary 4U 1636-53 with the Rossi X-Ray Timing Explorer (RXTE) for more than 1.5 years. Our campaign consisted of short (~2 ks) pointings separated by two days, regularly monitoring the spectral and timing properties of the source. During the campaign we observed a clear long-term oscillation with a period of ~30-40 days, already seen in the light curves from the RXTE All-Sky Monitor, which corresponded to regular transitions between the hard (island) and soft (banana) states. We detected kHz QPOs in about a third of the observations, most of which were in the soft (banana) state. The distribution of the frequencies of the peak identified as the lower kHz QPO is found to be different from that previously observed in an independent data set. This suggests that the kHz QPOs in the system shows no intrinsically preferred frequency.
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