# What is tc time at coalescence, ϕc phase at coalescence given in this following question ?for LIGO Data

I Am new to LIGO data

I was looking at the first solution for this question

How were the solar masses and distance of the GW150914 merger event calculated from the signal?

trying to reproduce a waveform for the LIGO merger. But I wasn't understanding the terms tc time at coalescence, ϕc phase at coalescence. I wanted to know how they can be determined by LIGO and how to use them to reproduce a waveform?

They have no meaning when taken individually. But if $t_c$ and $\phi_c$ are considered for multiple detectors it informs about the relative arrival time of wave at different detectors and hence is used to localize the origin of the source.