中国科学院紫金山天文台机构知识库

In the narrow-line Seyfert 1 galaxy Mrk 766, a quasi-periodic oscillation (QPO) signal with a period of similar to 6450 s is detected in the XMM-Newton data collected on 2005 May 31. This QPO signal is highly statistically significant at the similar to 5 sigma confidence level, with a quality factor of Q = f / Delta f > 13.6. The X-ray intensity changed by a factor of 3, with a root mean square fractional variability of 14.3%. Furthermore, this QPO signal is present in the data of all three EPIC detectors and two RGS cameras and its frequency follows the f(QPO)-M-BH relation spanning from stellar-mass to supermassive black holes. Interestingly, a possible QPO signal with a period of similar to 4200 s had been reported in the literature. The frequency ratio of these two QPO signals is similar to 3:2. Our result is also in support of the hypothesis that the QPO signals can just be transient. The spectral analysis reveals that the contribution of the soft excess component below similar to 1 keV is different between epochs with and without QPO. This property, as well as the former frequency ratio, are well-detected in X-ray BH binaries, which may shed some light on the physical origins of our event.