Transitional Dynamics: Unveiling the Coexistence and Interplay of Type-B and Type-C QPOs in MAXI J1348-630

TL;DR

This study uses broadband timing from Insight-HXMT and NICER to investigate MAXI J1348-630 during its 2019 outburst, uncovering brief coexistence and a competitive interaction between type-C and type-B QPOs. The type-C QPO dominates the hard X-ray band and suppresses the hard-band strength of the type-B QPO, while the two QPOs appear in distinct energy bands and evolve over two episodic coexistence periods. The results challenge the view of strictly rapid, exclusive transitions between QPO types and suggest a two-component accretion-jet geometry with energy-dependent variability modes, offering new insights into accretion state transitions and jet coupling in BHXRBs.

Abstract

Based on broadband timing analysis of Insight-HXMT and NICER data from the 2019 outburst of the black hole X-ray binary (BHXRB) MAXI J1348-630, we report the detection of the coexistence and competitive interplay between type-C and type-B quasi-periodic oscillations (QPOs). Specifically, the two QPO types were detected simultaneously but exhibited distinct energy dependencies: the type-C QPO was dominant in the hard X-ray band (10-30 keV), while the type-B QPO was more prominent in the soft X-ray band (1-10 keV). Further analysis reveals that the emergence of the type-C QPO suppresses the strength of the type-B QPO, particularly above 10 keV. Tracking the detailed evolution of these QPOs, we find that the weakening of the type-B QPO coincides with the strengthening of the type-C QPO, indicating a competitive interaction between them. These findings reveal a more complex relationship between type-B and type-C QPOs than previously recognized, suggesting they originate from distinct but interacting physical components within the accretion flow and/or jet, and providing new insights into the dynamics of accretion state transitions.

Figures (5)

• Figure 1: An overview of the light curves and QPO frequency evolution during the 2019 outburst of MAXI J1348-630 using Insight-HXMT data. In panel (b), the inset panels zoom in on the details around MJD 58527.5 and 58539.8, where type-C and type-B QPOs were simultaneously detected.
• Figure 2: Evolution of PDSs across the LE (upper) and ME (lower) bands from MJD 58527.4 to 58527.6. Type-B QPOs are marked with red dashed lines, and type-C QPOs are marked with blue dashed lines. From panel (1) to panel (2), the dominant noise type transitions to BLN (indicated by gray dashed lines), accompanied by the emergence of a $\sim$7.4 Hz type-C QPO (more prominent in ME) and the simultaneous detection of a $\sim$4.3 Hz type-B QPO (more prominent in LE).
• Figure 3: Correlation between the frequencies of type-C and type-B QPOs and the total fractional rms during the HS, HIMS and SIMS of the outburst. Simultaneously detected QPOs are marked with black boxes.
• Figure 4: Fractional rms spectra of type-B QPOs from three consecutive Insight-HXMT exposures. Among these panels, the middle one corresponds to the observation where a type-C QPO was detected simultaneously; the other two panels represent the preceding and following exposures, in which only type-B QPOs were detected.
• Figure 5: Evolution of PDSs around MJD 58539.8 in the soft (NICER, upper panels) and hard (ME, lower panels) X-ray bands. Type-B QPOs, type-C QPOs, and BLN are marked as in \ref{['fig:1702pds']}. In second column (panels (2) and (6)), a $\sim$7.4 Hz type-C QPO appears, coinciding with a strong BLN, while a type-B QPO is simultaneously detected at $\sim$4.9 Hz.