黑洞候选体MAXI J1535-571爆发期间的时变现象

利用“慧眼”(Hard X-ray Modulation Telescope, Insight-HXMT)卫星在2017年9月对黑洞候选体MAXI J1535-571的观测数据,研究了该源在爆发期内的时变现象.当源处于不同的爆发谱态时,功率密度谱的谱型存在明显差异.在硬中间态,有明显的限带噪声(band-limited noise)成分和QPO (Quasi-Periodic Oscillation)成分.分析结果表明:低频限带噪声的特征频率随能量的变化呈现正相关,即软能段光子的特征频率小于硬能段光子的特征频率. 0.1–0.5 Hz频率区间的限带噪声RMS (Root Mean Square)谱在硬中间态和软中间态均出现峰值,且在高能端存在差异,可能是主导噪声RMS的能谱成分占比不同.当谱态由硬中间态过渡到软中间态时, C型QPO的RMS谱保持相似趋势,但限带噪声RMS谱存在谱态依赖现象,暗示着噪声和QPO有不同的起源机制.

The Temporal Phenomena during the Outburst of the Black Hole Candidate MAXI J1535-571

Using the observations of the black hole candidate MAXI J1535-571 by the Hard X-ray Modulation Telescope (Insight-HXMT) in September 2017, the temporal phenomena of the source during the outburst period are studied. There are significant differences in the power density spectra when the source is in different outburst states. And in the hard intermediate state, there are obvious band-limited noise components and QPO (Quasi-Periodic Oscillation) components. The analysis results show that the characteristic frequency of low frequency band-limited noise is positively correlated with the energy, i.e. the characteristic frequency of photons in soft energy band is less than that in hard energy band. The band-limited noise RMS (Root Mean Square) spectra in the 0.1--0.5Hz show peaks in both the hard and soft intermediate states, and there are differences at the high energy, probably due to the ratio of the energy spectrum components of the dominant noise RMS is different. The type-C QPO RMS spectrum maintains a similar trend when the spectral state is from the hard intermediate state to the soft intermediate state. But there is a spectral state dependence in the band-limited noise RMS spectrum, implying that the noise and QPO have different mechanisms of origin.