Choosing the start time of binary black hole ringdown
This talk will broadly explore the question of finding the onset of binary black hole (BBH) ringdown (RD) in BBH merger data and waveforms. RD refers to the final stage of a BBH merger in which the system is described by a Kerr BH with quasi normal mode (QNM) perturbations. Being in this regime allows one to perform certain tests of general relativity, including tests of the no-hair theorem. However, determining when in a BBH waveform this regime occurs is non-trivial. I will describe past efforts to determine this start time, and talk about recent work attempting to use information from the strong-field region to inform this start time, and present results in the context of GW150914.