August 11, 2025Open Access

Detection of Multiple X-Ray Quasi-periodic Oscillations in IGR J19294+1816 with Insight-HXMT

WYWen YangChina Building Materials Academy WWWei WangEast China University of Science and Technology

Key Points

Multiple quasi-periodic oscillations (QPOs) were detected at around 30 mHz and 50 mHz, indicating unique pulsar dynamics.
The analysis showed a significant QPO feature at approximately 30.2 mHz with rms amplitude peaking at 12% in the 25–50 keV range.
Wavelet analysis identified transient behaviors in QPO frequencies around 30, 51.1, and 113.7 mHz during the timing observations.
Our findings establish IGR J19294+1816 as a strong magnetic field pulsar, prompting investigation into potential physical origins of the observed QPOs.

Abstract

Abstract We report the timing results with Insight-HXMT observations of X-ray binary IGR J19294+1816 during its 2019 type I outburst at the decline phase shortly following its peak. We analyze the light curves and power density spectrum of the 2019 observations and reveal a peak at ν NS ∼ 80.2 mHz, corresponding to X-ray pulsations from the neutron star. In addition, a significant quasi-periodic oscillation (QPO) feature is observed at ν QPO ∼ 30.2 mHz from 10 to 50 keV, with the rms amplitude increasing with energy. Furthermore, we detect two QPOs at frequencies of ∼51.1 and 113.7 mHz (corresponding to sidebands near ν NS ± ν QPO ) in the range 25–50 keV, exhibiting an rms amplitude of around 12%. Wavelet analysis also shows multiple QPOs at the frequencies of ∼30 mHz, 50 and 110 mHz, which have transient behaviors. The centroid frequencies of ∼30 mHz remain nearly constant for different luminosities. Our research identifies IGR J19294+1816 as the second strong magnetic field pulsar with significant sideband signals around the spin frequency. We explore various physical origins that could explain the presence of multiple QPOs.

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