Item

Abstract

Full, non-linear general relativity predicts a memory effect for
gravitational waves. For compact binary coalescence, the total gravitational
memory serves as an inferred observable, conceptually on the same footing as
the mass and the spin of the final black hole. Given candidate waveforms for
any LIGO event, then, one can calculate the posterior probability distribution
functions for the total gravitational memory, and use them to compare and
contrast the waveforms. In this paper we present these posterior distributions
for the binary black hole merger events reported in the first Gravitational
Wave Transient Catalog (GWTC-1), using the Phenomenological and
Effective-One-Body waveforms. On the whole, the two sets of posterior
distributions agree with each other quite well though we find larger
discrepancies for the $\ell=2, m=1$ mode of the memory. This signals a possible
source of systematic errors that was not captured by the posterior
distributions of other inferred observables. Thus, the posterior distributions
of various angular modes of total memory can serve as diagnostic tools to
further improve the waveforms. Analyses such as this would be valuable
especially for future events as the sensitivity of ground based detectors
improves, and for LISA which could measure the total gravitational memory
directly.