Gravitational wave detection from OJ 287 via a pulsar timing array

TL;DR

This study assesses the potential for pulsar timing arrays to detect gravitational waves from the blazar OJ 287, analyzing expected signals, pulsar contributions, and parameter measurement prospects over a decade.

Contribution

It provides a detailed prediction of GW signals from OJ 287 and evaluates the detection capabilities of current and future PTAs, highlighting the role of specific pulsars like PSR J0437-4715.

Findings

GW strain from OJ 287 peaks at 8×10^{-16} before 2021

Total SNR of PTA ranges from 1.9 to 2.9 over 10 years

PSR J0437-4715 can constrain polarization angle with <8° uncertainty

Abstract

Blazar OJ 287 is a candidate nanoHertz (nHz) gravitational wave (GW) source. In this article, we investigate the GWs generated by OJ 287 and their potential detection through a pulsar timing array (PTA). First, we obtain the orbit and the corresponding GW strain of OJ 287. During the time span of the next 10 years (2019 to 2029), the GW of OJ 287 will be active before 2021, with a peak strain amplitude $8 \times 10^{-16}$, and then decay after that. When OJ 287 is silent in the GW channel during 2021 to 2029, the timing residual signals of the PTA will be dominated by the 'pulsar term' of the GW strain and this provides an opportunity to observe this pulsar term. Furthermore, we choose 26 pulsars with white noise below 300 ns to detect the GW signal of OJ 287, evaluating their timing residuals and signal-to-noise ratios (SNRs). The total SNR (with a cadence of 2 weeks in the next 10 years) of the PTA ranges from 1.9 to 2.9, corresponding to a weak GW signal for the current sensitivity level. Subsequently, we investigate the potential measurement of the parameters of OJ 287 using these pulsars. In particular, PSR J0437-4715, with a precisely measured distance, has the potential to constrain the polarization angle with an uncertainty below $8^{\deg}$ and this pulsar will play an important role in future PTA observations.