Multimessenger Approaches to Supermassive Black Hole Binary Detection and Parameter Estimation II: Optimal Strategies for a Pulsar Timing Array

TL;DR

This paper evaluates optimal strategies for pulsar timing arrays to detect and precisely estimate parameters of supermassive black hole binaries identified through electromagnetic signals, enhancing multi-messenger astronomy.

Contribution

It demonstrates that an all-sky PTA observing the best pulsars is optimal for detecting EM-selected SMBHBs and achieving high-precision parameter estimation.

Findings

All-sky PTA with top pulsars is effective for SMBHB detection.

PTA can measure SMBHB parameters with precision comparable to electromagnetic methods.

Implications for future multi-messenger observations with planned PTA experiments.

Abstract

Pulsar timing arrays (PTAs) are Galactic-scale gravitational wave (GW) detectors consisting of precisely-timed pulsars distributed across the sky. Within the decade, PTAs are expected to detect the nanohertz GWs emitted by close-separation supermassive black hole binaries (SMBHBs), thereby opening up the low frequency end of the GW spectrum for science. Individual SMBHBs which power active galactic nuclei are also promising multi-messenger sources; they may be identified via theoretically predicted electromagnetic (EM) signatures and be followed up by PTAs for GW observations. In this work, we study the detection and parameter estimation prospects of a PTA which targets EM-selected SMBHBs. Adopting a simulated Galactic millisecond pulsar population, we envisage three different pulsar timing campaigns which observe three mock sources at different sky locations. We find that an all-sky PTA which times the best pulsars is an optimal and feasible approach to observe EM-selected SMBHBs and measure their source parameters to high precision (i.e., comparable to or better than conventional EM measurements). We discuss the implications of our findings in the context of the future PTA experiment with the planned Deep Synoptic Array-2000 and the multi-messenger studies of SMBHBs such as the well-known binary candidate OJ 287.