Phase-resolved QPO Analysis of GX 339-4: Improved Technique and Consistent Behaviors between QPOs and Broadband Noise
Abstract
The nature of low-frequency quasi-periodic oscillations (QPOs) in black hole X-ray binaries remains unclear, and their relationship with the accompanying broadband noise (BBN) is still under debate. Here, we propose an improved variational mode decomposition (VMD) technique. Compared with the original algorithm that requires iterative, case-by-case parameter tuning, the new algorithm automatically and consistently determines the relevant VMD parameters based on the QPO central frequency and width measured from the power spectral density (PSD). This enables a more robust phase determination for QPOs and can also be applied to the study of BBN. We found that, for low-frequency type-C QPOs without significant harmonics in the black hole X-ray binary GX 339-4, the spectral properties of the QPOs and BBN are statistically consistent with each other: (1) the photon index is positively correlated with count rate as a function of phase, and (2) the PSD ratio spectra across different energy bands show no statistically significant QPO-like structures near the QPO frequencies, indicating that both components share the same energy dependence. These suggest that QPOs and BBN may be driven by the same physical processes. The QPO models based on geometric modulation struggle to account for the results, while those invoking corona oscillations are favored.
Versions
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BibTeX
@misc{qin2026phaseresolved,
title = {{Phase-resolved QPO Analysis of GX 339-4: Improved Technique and Consistent Behaviors between QPOs and Broadband Noise}},
author = {Jin Qin and Hua Feng and Liang Zhang and Lian Tao and Qing-Cang Shui and Qing-Chang Zhao and Shu Zhang and Shuang-Nan Zhang},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.05916},
eprint = {2608.05916},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.05916},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Phase-resolved QPO Analysis of GX 339-4: Improved Technique and Consistent Behaviors between QPOs and Broadband Noise
AU - Jin Qin
AU - Hua Feng
AU - Liang Zhang
AU - Lian Tao
AU - Qing-Cang Shui
AU - Qing-Chang Zhao
AU - Shu Zhang
AU - Shuang-Nan Zhang
PY - 2026
DA - 2026/08/06
PB - arXiv
DO - 10.48550/arxiv.2608.05916
UR - https://arxiv.org/abs/2608.05916
AB - The nature of low-frequency quasi-periodic oscillations (QPOs) in black hole X-ray binaries remains unclear, and their relationship with the accompanying broadband noise (BBN) is still under debate. Here, we propose an improved variational mode decomposition (VMD) technique. Compared with the original algorithm that requires iterative, case-by-case parameter tuning, the new algorithm automatically and consistently determines the relevant VMD parameters based on the QPO central frequency and width measured from the power spectral density (PSD). This enables a more robust phase determination for QPOs and can also be applied to the study of BBN. We found that, for low-frequency type-C QPOs without significant harmonics in the black hole X-ray binary GX 339-4, the spectral properties of the QPOs and BBN are statistically consistent with each other: (1) the photon index is positively correlated with count rate as a function of phase, and (2) the PSD ratio spectra across different energy bands show no statistically significant QPO-like structures near the QPO frequencies, indicating that both components share the same energy dependence. These suggest that QPOs and BBN may be driven by the same physical processes. The QPO models based on geometric modulation struggle to account for the results, while those invoking corona oscillations are favored.
ER -