2025ApJ...988..115Y

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.