# Measuring Spin of the Remnant Black Hole from Maximum Amplitude

## TL;DR

This paper introduces a new, template-independent method to measure the spin of the remnant black hole from gravitational wave data at the peak amplitude, using only the chirp mass and strain frequency information.

## Contribution

The paper proposes a novel technique to determine the remnant black hole's spin directly at peak amplitude without relying on templates, simplifying analysis.

## Key findings

- Remnant black hole spin can be estimated at peak amplitude.
- Method is independent of gravitational wave templates.
- Accurate spin measurement is possible using strain frequency and its derivative.

## Abstract

Gravitational waves emitted during the merger of two black holes carry information about the remnant black hole, namely its mass and spin. This information is typically found from the ringdown radiation as the black hole settles to a final state. We find that the remnant black hole spin is already known at the peak amplitude of the gravitational wave strain. Using this knowledge, we present a new method for measuring the final spin that is template independent, using only the chirp mass, the instantaneous frequency of the strain and its derivative at maximum amplitude, all template independent.