Transitions and Origin of the Type-B Quasi-Periodic Oscillation in the Black Hole X-ray Binary MAXI~ J1348--630

H. X. Liu, Y. Huang, Q. C. Bu, W. Yu, Z. X. Yang, L. Zhang, L. D. Kong, G. C. Xiao, J. L. Qu, S. N. Zhang, S. Zhang, L. M. Song, S. M. Jia, X. Ma, L. Tao, M. Y. Ge, Q. Z. Liu, J. Z. Yan, R. C. Ma, X. Q. Ren, D. K. Zhou, T. M. Li, B. Y. Wu, Y. C. Xu, Y. F. Du, Y. C. Fu, Y. X. Xiao, G. Q. Ding, X. X. Yu

Published 2022-08-15Version 1

The fast transitions between different types of quasi-periodic oscillations (QPOs) are generally observed in black hole transient sources (BHTs). We present a detailed study on the timing and spectral properties of the transitions of type-B QPOs in MAXI~J1348--630, observed by \emph{Insight}-HXMT. The fractional rms variability--energy relationship and energy spectra reveal that type-B QPOs probably originate from jet precession. Compared to weak power-law dominated power spectrum, when type-B QPO is present, the corresponding energy spectrum shows an increase in Comptonization component and the need for {\tt\string xillverCp} component, and a slight increase of height of the corona when using {\tt\string relxilllp} model. Therefore, we suggest that a coupled inner disk-jet region is responsible for the observed type-B QPOs transitions. The time scale for the appearance/disappearance of type-B QPOs is either long or short (seconds), which may indicate an instability of disk-jet structure. For these phenomena, we give the hypothesis that the Bardeen-Petterson effect causes disk-jet structure to align with BH spin axis, or that the disappearance of small-scale jets bound by the magnetic flux tubes lead to the disappearance of type-B QPOs. We observed three events regarding the B/C transitions, one of which occurred in a short time from $\sim 9.2$ Hz (C) to $\sim 4.8$ Hz (B). The energy spectral analysis for the other two transitions shows that when type-C QPO is present, the Comptonization flux is higher, the spectrum is harder and the inner radius of disk changes insignificantly. We suggest that type-C QPOs probably originate from relatively stronger jets or corona.