Evolution of QPOs in GX 339–4 and EXO 1846–031 with Insight-HXMT and NICER

We conduct a spectral and timing analysis of GX 339−4 and EXO 1846−031 with the aim of studying the evolution of type-C quasiperiodic oscillations (QPOs) with spectral parameters. The high-cadence data from Insight-HXMT and NICER allow us to track the evolution of QPOs and spectra simultaneously. Type-C QPOs appear at the end of the low–hard state and/or the hard–intermediate state. Our results reveal that the QPO frequency is closely related to the inner disk radius and mass accretion rate in the two sources. This correlation aligns well with the dynamic frequency model of a truncated disk.