Adding Gravitational Memory to Waveform Catalogs using BMS Balance Laws

TL;DR

This paper introduces a method to incorporate gravitational memory effects into existing waveform catalogs by applying BMS balance laws, improving waveform accuracy and consistency with CCE results, and providing open-source tools for the community.

Contribution

The authors develop a correction technique using BMS balance laws to add gravitational memory to waveform catalogs, enhancing their physical accuracy and consistency with independent methods.

Findings

Corrected waveforms satisfy BMS balance laws more accurately.

Corrected waveforms align well with CCE waveforms exhibiting memory.

The method reduces transient junk effects in waveform data.

Abstract

Accurate models of gravitational waves from merging binary black holes are crucial for detectors to measure events and extract new science. One important feature that is currently missing from the Simulating eXtreme Spacetimes (SXS) Collaboration's catalog of waveforms for merging black holes, and other waveform catalogs, is the gravitational memory effect: a persistent, physical change to spacetime that is induced by the passage of transient radiation. We find, however, that by exploiting the Bondi-Metzner-Sachs (BMS) balance laws, which come from the extended BMS transformations, we can correct the strain waveforms in the SXS catalog to include the missing displacement memory. Our results show that these corrected waveforms satisfy the BMS balance laws to a much higher degree of accuracy. Furthermore, we find that these corrected strain waveforms coincide especially well with the waveforms obtained from Cauchy-characteristic extraction (CCE) that already exhibit memory effects. These corrected strain waveforms also evade the transient junk effects that are currently present in CCE waveforms. Lastly, we make our code for computing these contributions to the BMS balance laws and memory publicly available as a part of the python package $\texttt{sxs}$, thus enabling anyone to evaluate the expected memory effects and violation of the BMS balance laws.