标题： RossiXTE对4U 1636-53的监测：I. 长期演化和kHz准周期振荡 显示英文标题

标题： RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations

摘要： 我们使用Rossi X-Ray Timing Explorer (RXTE) 对环礁型中子星低质量X射线双星4U 1636-53进行了超过1.5年的监测。我们的观测活动包括每隔两天的短时间（约2 ks）指向，定期监测该天体的光谱和定时特性。在观测期间，我们观察到一个清晰的长期振荡，周期约为30-40天，这已在RXTE全天空监视器的光变曲线中被观察到，对应于硬（岛状）态和软（香蕉）态之间的常规转换。我们在大约三分之一的观测中检测到了kHz QPOs，其中大部分出现在软（香蕉）态。发现被识别为下kHz QPO的峰频率分布与之前在独立数据集中观察到的有所不同。这表明该系统中的kHz QPOs没有固有的首选频率。 显示英文摘要

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.