2024ApJ...969..152W

Based on the Insight-HXMT archival data, we have detected a new atypical low-frequency quasiperiodic oscillation (LFQPO) in the black hole X-ray binary MAXI J1348-630. The new LFQPO is detected in all three instruments of Insight-HXMT with a combined significance of 3σ-5σ, covering a wide energy range of 1-100 keV. The fractional rms seems to decrease with energy. It exclusively appears in the hard state during both the main and mini outburst, spanning an X-ray intensity range by a factor of 10, and a very narrow hardness range. The frequency of this new type of LFQPO is moderately stable, in the range of 0.08-0.15 Hz. We discussed different models for the LFQPO, and found none can explain the observed properties of this new type of LFQPO.