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arXiv · 2201.08588

Evolution of Accretion Modes between Spectral States Inferred from Spectral and Timing Analysis of Cygnus X-1 with Insight-HXMT observations

M. Z. Feng·L. D. Kong·P. J. Wang·S. N. Zhang·H. X. Liu·Z. X. Yang·Y. Huang·L. Ji·S. M. Jia·X. Ma·W. Yu·H. S. Zhao·J. Y. Nie·Y. L. Tuo·S. Zhang·J. L. Qu·B. B. Wu
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Abstract

We execute a detailed spectral-timing study of Cygnus X-1 in the low/hard, intermediate and high/soft states with the Hard X-ray Modulation Telescope observations. The broad band energy spectra fit well with the "truncated disk model" with the inner boundary of the accretion disk stays within $\sim$10 \textit R$_{\rm g}$ and moves inward as the source softens. Through studying of PDS, rms and Fourier-frequency component resolved spectroscopy, we find that the X-ray variations are generated in two different regions for each state. We discover that the major role that contributes to the X-ray variation is the hot corona rather than the accretion disk. We suggest a scenario with different corona geometry for each state based on the truncated disk geometry in which the corona wraps up the disk to form a sandwich geometry in the low/hard state, and then gradually moves away from the disk in direction that is perpendicular to the disk until forming a jet-like geometry in the high/soft state.

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M. Z. Feng, L. D. Kong, P. J. Wang, S. N. Zhang, H. X. Liu, Z. X. Yang, Y. Huang, L. Ji, S. M. Jia, X. Ma, W. Yu, H. S. Zhao, J. Y. Nie, Y. L. Tuo, S. Zhang, J. L. Qu, B. B. Wu. 2022-01-21. Evolution of Accretion Modes between Spectral States Inferred from Spectral and Timing Analysis of Cygnus X-1 with Insight-HXMT observations. https://doi.org/10.3847/1538-4357/ac7875

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