# Comparison and contrast of test-particle and numerical-relativity waveform templates

## TL;DR

This paper compares gravitational waveforms from a test-particle model around a Kerr black hole with numerical relativity templates for black hole mergers, revealing surprising agreement under certain assumptions.

## Contribution

It introduces a novel comparison between test-particle waveforms and numerical relativity templates, highlighting unexpected agreements and raising questions about effective parameters.

## Key findings

- Surprising agreement between models under specific assumptions
- Effective Kerr spin parameter plays a key role
- Insights into waveform modeling for black hole mergers

## Abstract

We compare and contrast the emission of gravitational waves and waveforms for the recently established "helicoidal-drifting-sequence" of a test particle around a Kerr black hole with the publicly available waveform templates of numerical-relativity. The merger of two black holes of comparable mass are considered. We outline a final smooth merging of the test particle into the final Kerr black hole. We find a surprising and unexpected agreement between the two treatments if we adopt, for the mass of the particle and the Kerr black hole a Newtonian-center-of-mass description, and for the Kerr black hole spin an effective value whose nature remains to be clarified.