Search for Memory and Inspiral Gravitational Waves from Super-Massive Binary Black Holes with Pulsar Timing Arrays

TL;DR

This paper investigates the potential for pulsar timing arrays to detect gravitational wave memory and inspiral signals from super-massive binary black holes, estimating low detection probabilities despite upcoming telescope improvements.

Contribution

It provides the first estimates of detection rates for GW memory and inspiral signals from SBBHs with PTAs and offers scaling relations for future studies.

Findings

Detection probability for GW memory and inspiral signals is less than one with current and planned PTAs.

Scaling relations are developed to assess detection probabilities of GWs from SBBHs.

Even with the Square Kilometer Array, detection of these signals remains unlikely.

Abstract

The merger of a super-massive binary black hole (SBBH) is one of the most extreme events in the universe with a huge amount of energy released by gravitational radiation. Although the characteristic gravitational wave (GW) frequency around the merger event is far higher than the nHz regime optimal for pulsar timing arrays (PTAs), nonlinear GW memory might be a critical smoking gun of the merger event detectable with PTAs. In this paper, basic aspects of this interesting observation are discussed for SBBHs, and the detection numbers of their memory and inspiral GWs are estimated for ongoing and planned PTAs. We find that the expected detection number would be smaller than unity for the two-types of signals even with the Square Kilometer Array. We also provide various scaling relations that would be useful to study detection probabilities of GWs from individual SBBHs with PTAs.