Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The full evolution of the type-C QPO in MAXI J1348-630 revealed by Insight-HXMT

X. -L. Wang, Z. Yan, F. -G. Xie, J. -F. Wang, Y. -X. Li, Z. -Y. Liu, R. -Y. Ma

Abstract

Based on abundant data from Insight-HXMT, we conducted a detailed analysis of type-C quasi-periodic oscillations (QPOs) in the black hole X-ray binary MAXI J1348-630. Type-C QPOs were intensively detected over a broad energy band, with frequencies ranging from 0.24 to 10.3 Hz, and several new evolutionary features were identified. First, although type-C QPOs reappear intermittently, they show a stable characteristic frequency around 7 Hz. This implies a characteristic spatial scale for the QPO emission region, despite large variations in outburst intensity. Second, from the hard state to the hard-intermediate state, type-C QPOs display a harder fractional rms spectrum, with the rms peak shifting toward high energies (>20 keV) and an amplitude exceeding 10 %. This hard rms spectrum favors a high-energy origin for type-C QPOs. The spectral hardening occurs simultaneously with the weakening of the compact jet, suggesting a physical connection between these two processes. Finally, we observed hysteresis in the QPO frequency-flux relation, with the hysteresis loop evolving in opposite directions between the main and mini-outbursts. This offers a new perspective on the physical differences between the two outburst types, which may arise from variations in initial magnetic field conditions.

The full evolution of the type-C QPO in MAXI J1348-630 revealed by Insight-HXMT

Abstract

Based on abundant data from Insight-HXMT, we conducted a detailed analysis of type-C quasi-periodic oscillations (QPOs) in the black hole X-ray binary MAXI J1348-630. Type-C QPOs were intensively detected over a broad energy band, with frequencies ranging from 0.24 to 10.3 Hz, and several new evolutionary features were identified. First, although type-C QPOs reappear intermittently, they show a stable characteristic frequency around 7 Hz. This implies a characteristic spatial scale for the QPO emission region, despite large variations in outburst intensity. Second, from the hard state to the hard-intermediate state, type-C QPOs display a harder fractional rms spectrum, with the rms peak shifting toward high energies (>20 keV) and an amplitude exceeding 10 %. This hard rms spectrum favors a high-energy origin for type-C QPOs. The spectral hardening occurs simultaneously with the weakening of the compact jet, suggesting a physical connection between these two processes. Finally, we observed hysteresis in the QPO frequency-flux relation, with the hysteresis loop evolving in opposite directions between the main and mini-outbursts. This offers a new perspective on the physical differences between the two outburst types, which may arise from variations in initial magnetic field conditions.
Paper Structure (13 sections, 6 figures)

This paper contains 13 sections, 6 figures.

Table of Contents

  1. Introduction
  2. MAXI J1348$-$630
  3. Observation and data analysis
  4. Results
  5. Frequency evolution of type-C QPO
  6. Fractional rms evolution of type-C QPO
  7. Correlation between type-C QPO and X-ray flux
  8. Discussion
  9. The stable reappearance frequency at $\sim$7 Hz
  10. The hardening of the fractional rms spectra
  11. Hysteresis loops in flux-frequency diagram
  12. Conclusion
  13. Data availability

Figures (6)

  • Figure 1: Evolution of (a) the count rate, (b) the centroid frequency, and (c) the fractional rms of the type-C QPO as observed with the three Insight-HXMT instruments. For comparison, the frequencies of type-A QPOs reported by zhang_2023 are also plotted in panel (b) (magenta triangles). Vertical brown dashed lines demarcate the different states during the main and mini-outbursts.
  • Figure 2: (a) HID, where the count rate is measured in the 1--10 keV band and the hardness is defined as the ratio of the 10--30 keV to the 1--10 keV count rates; gray pentagrams mark the detections of type-C QPOs. (b) RID, where the fractional rms is calculated over the 0.5--64 Hz frequency range in the 1--10 keV band. (c) Type-C QPO frequency versus the total fractional rms (computed in the 1--10 keV band over 0.5--64 Hz). In all three panels, different colors represent different spectral states.
  • Figure 3: Representative PDSs in the LE, ME, and HE bands during different outburst states. The blue dashed lines indicate the fitted type-C QPO components.
  • Figure 4: Evolution of the fractional rms spectrum of type-C QPO. Each panel is labeled in the upper-right corner with the observation date, spectral state, and type-C QPO frequency.
  • Figure 5: Representative spectra observed in the rise-HS (panel a), rise-HIMS (panel b) and mini-outburst (panel c). The data points with error bars correspond to the Insight-HXMT LE (blue), ME (orange), and HE (green) observations. The solid black line represents the best-fitting total model, while the dashed lines indicate the individual components: the accretion disk (red), Comptonization (blue), and reflection (cyan), respectively.
  • ...and 1 more figures