Cyg X-2 was observed by the Rossi X-Ray Timing Explorer during in-orbit checkout in 1996 January and was found in the horizontal, normal, and flaring branches. Horizontal-branch quasi-periodic oscillations were seen with an rms variability of approximately 6% in the fundamental. The second harmonic was also seen with an rms variability about three-fourths that of the fundamental. In the course of 2 hr, the centroid frequency of the fundamental ranged from 17 to 22 Hz, with significant variations on timescales of tens of seconds, and it was positively correlated with source intensity in the 0-20 keV band. The ratio of the width of the fundamental to its centroid frequency was 0.15-0.2. The centroid and width of the second harmonic were 2 times those of the fundamental. The relative positions of the fundamental and harmonic, as well as their correlation with intensity, are consistent with the beat-frequency-modulated accretion Model of the quasi-periodic oscillation, which predicts a magnetic field of 2.2 X 10~9 G and a spin frequency of 165 Hz for the neutron star. The relative widths of the two peaks and the time history of the fundamental frequency suggest that the observed width of the peaks is due to More than temporal variation of the frequency.
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机译：Cyg X-2是在1996年1月由罗西X射线定时探测器在轨道上结帐时观测到的，并在水平，正常和张开的分支中发现。可以看到水平分支的准周期振荡，其基波均方根变化约为6％。还可以看到二次谐波的均方根变化约为基频的四分之三。在2小时的过程中，基波的质心频率范围为17到22 Hz，在数十秒的时间尺度上有显着变化，并且它与0-20 keV频带中的源强度呈正相关。基频的宽度与其质心频率的比值为0.15-0.2。二次谐波的质心和宽度是基波的质心和宽度的2倍。基波和谐波的相对位置，以及它们与强度的关系，与准周期振荡的拍频调制增生模型一致，该模型预测了2.2 X 10〜9 G的磁场和自旋中子星的频率为165 Hz。两个峰的相对宽度和基本频率的时程表明，观察到的峰宽是由于频率的瞬时变化所致。
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