Importance of mirror modes in binary black hole ringdown waveform

Understand

The post-merger signal in binary black hole merger is described by linear, black-hole perturbation theory.

• Historically, this has been modeled using the dominant positive-frequency (corotating) fundamental mode.
• Recently, there has been a renewed effort in modeling the post-merger waveform using higher, positive-frequency overtones in an attempt to achieve greater accuracy in describing the waveform at earlier times using linear perturbation theory.
• It has been shown that the inclusion of higher overtones can shift the linear regime to the peak of $(l,m)=(2,2)$ spherical harmonic mode.