Application of the Hilbert-Huang transform for analyzing standing-accretion-shock-instability induced gravitational waves in a core-collapse supernova

Through numerical simulations, it is predicted that the gravitational waves (GWs) reflect characteristics of core-collapse supernova (CCSN) explosion mechanism. There are multiple GW excitation processes occur inside a star before its explosion, and suggested GWs originating from CCSN have mode for each process in terms time-frequency representation. Therefore, we propose an application Hilbert-Huang Transform (HHT), which high-resolution analysis method, to analyze these modes theoretically probing increasing our understanding The HHT defines frequency as function time, not bound by trade-off between time resolutions. In this study, waveform obtained three-dimensional general-relativistic model showed vigorous activity standing-accretion-shock-instability (SASI). We succeed extracting SASI induced with high resolution on representation using examine their instantaneous frequencies.