Post-merger chirp morphology and parameterization

The gravitational waves produced by binary black hole systems with an asymmetric mass ratio have been shown to exhibit a characteristic double-chirp pattern when viewed from a highly inclined orientation. These chirp patterns are composed of mixed higher-order modes produced during the ringdown, due to regions of high curvature on the distorted apparent horizon. Herein we motivate a means to reduce the double-chirp phenomenon into a single-number parameter that describes its strength relative to that of the overall signal. This is accomplished by adapting a continuous wavelet transform scan to utilize a chirplet (a Sine-Guassian wavelet with a forward chirp rate) as the mother wavelet, enhancing the contrast of the spectrogram. The development of this technique is discussed, along with prospects towards mapping the apparent horizon evolution.