Quasi-periodic oscillations under wavelet microscope: the application of Matching Pursuit algorithm

Understand

We zoom in on the internal structure of the low-frequency quasi-periodic oscillation (LF QPO) often observed in black hole binary systems to investigate the physical nature of the lack of coherence in this feature.

• We show the limitations of standard Fourier power spectral analysis for following the evolution of the QPO with time and instead use wavelet analysis and a new time-frequency technique -Matching Pursuit algorithm- to maximise the resolution with which we can follow the QPO behaviour.
• We use the LF QPO seen in a very high state of XTE J1550-564 to illustrate these techniques and show that the best description of the QPO is that it is composed of multiple independent oscillations with a distribution of lifetimes but with constant frequency over this duration.
• This rules out models where there is continual frequency modulation, such as multiple blobs spiralling inwards.