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arXiv · 2306.13994

Quasi-periodic oscillations in GX 339-4 during the 2021 Outburst observed with Insight-HXMT

Y. J. Jin·W. Wang·X. Chen·P. F. Tian·Q. Liu·P. Zhang·H. J. Wu·N. Sai
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Abstract

A new outburst of GX 339$-$4 in 2021 was monitored by the Hard X-ray Modulation Telescope (\textit{Insight}-HXMT). By using the data of \textit{Insight}-HXMT from February to March 2021, we make the X-ray timing analysis of this new outburst. Based on the results of count rates, hardness-intensity diagram (HID) and power density spectrum (PDS), we confirm that the source exhibits spectral transitions from the low-hard state (LHS) to the hard-intermediate state (HIMS). During the transition from the LHS to the HIMS, Low-frequency Quasi-periodic oscillations (LFQPOs) are detected in the PDS. We found that these QPOs are all type-C QPOs with centroid frequencies evolving from $0.1 -0.6$ Hz in the LHS and in the $1 -3$ Hz frequency range in HIMS. The QPO features above 50 keV are reported for the first time in this black hole by \textit{Insight}-HXMT. The QPO rms stays stable with time but decreases with energy at higher energy above $\sim 10$ keV. We also find that the phase lag of the type-C QPO is close to zero in the early outburst stage, but becomes positive as the outburst evolves, with a hard lag of $\sim$ 0.6-1.2 rad in $50 -100 $ keV. The implications of the phase lag in high energy bands and possible physical mechanisms to explain those observations are also discussed.

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Y. J. Jin, W. Wang, X. Chen, P. F. Tian, Q. Liu, P. Zhang, H. J. Wu, N. Sai. 2023-06-24. Quasi-periodic oscillations in GX 339-4 during the 2021 Outburst observed with Insight-HXMT. https://doi.org/10.3847/1538-4357%2Face168

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