Search for Gravitational Wave Memory in PPTA and EPTA Data: A Complete Signal Model

TL;DR

This paper searches for gravitational wave memory signals in PTA data, developing models for SMBHB mergers and generic bursts, and sets upper limits on their occurrence and strain amplitudes.

Contribution

It introduces the first search for SMBHB merger memory using full numerical relativity waveforms and explores computationally efficient methods for burst searches.

Findings

Ruled out SMBHB mergers with chirp mass 10^10 Solar Mass up to 700 Mpc

Set upper limits on displacement memory burst amplitudes > 10^-14

Developed new models and methods for gravitational wave memory searches

Abstract

We perform searches for gravitational wave memory in the data of two major Pulsar Timing Array (PTA) experiments located in Europe and Australia. Supermassive black hole binaries (SMBHBs) are the primary sources of gravitational waves in PTA experiments. We develop and carry out the first search for late inspirals and mergers of these sources based on full numerical relativity waveforms with null (nonlinear) gravitational wave memory. Additionally, we search for generic bursts of null gravitational wave memory, exploring possibilities of reducing the computational cost of these searches through kernel density and normalizing flow approximation of the posteriors. We rule out the mergers of SMBHBs with a chirp mass of 10^10 Solar Mass up to 700 Mpc over 18 years of observation at 95% credibility. We rule out the observation of generic displacement memory bursts with strain amplitudes > 10^-14 in brief periods of the observation time but across the sky, or over the whole observation time but for certain preferred sky positions, at 95%$credibility.