Promise of Persistent Multi-Messenger Astronomy with the Blazar OJ 287

Abstract

Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades.

Characterizing Optical Variability of OJ 287 in 2016–2017

“…It should be noted that the lack of observations before MJD ∼ 57650 allow an ambiguity of ±180 • in representation of PA. In our presentation of the PA changes here we chose a smooth variation over a big jump, and so it differs by 180 • to the presentation of some similar data Valtonen et al (2017). The choice is based on the fact the PD variation seen here is almost always associated with PA change and the fact that the fractional polarization shows both systematic and chaotic trends.…”

“…Valtonen et al (2008aValtonen et al ( , 2010 explain the deviations of the outbursts from strict periodicity as arising from this gravitational wave driven in-spiraling of the binary black hole system present at the centre of OJ 287. According to the latest iteration of the model, the source is an inspiraling and precessing binary SMBH system with a current period of 12.055 years which decreases by 38 days/century and involves a minimum separation of 1.1 years between the twin outbursts associated with the disk impacts (Valtonen et al 2017).…”

A possible tidal disruption event candidate in the black hole binary system of OJ 287

“…The outburst during 2016-2017 was reported and studied before (Rakshit et al 2017;Siejkowski & Wierzcholska 2017;Komossa et al 2017), and it was explained as the post-effect of secondary black hole impacted on disc (Valtonen et al 2017;Kushwaha et al 2018;Gupta et al 2019;Komossa et al 2020Komossa et al , 2021 or combination of shock and the jet's precession (Kapanadze et al 2018). In this section, we discuss the three origins of the outburst, including jet's precession, post-effect of black hole-disc impaction and TDE.…”

“…Hence, the optical light curves manifest a doublepeaked structure seen in the 12 year quasi-periodic outbursts (Lehto & Valtonen 1996). When the perturbation caused by the impact event propagates in the accretion disc, the accretion rate may be affected, hence additional fluctuations in the light curves due to shock in jet occur (Pihajoki et al 2013;Valtonen et al 2017;Kushwaha et al 2018;Kapanadze et al 2018;Komossa et al 2020Komossa et al , 2021.…”

“…However, one possibility for OJ 287 faint in X-ray before is that the lack of intensive X-ray observations in history may lead to miss some extreme X-ray outbursts. Moreover, the timing of the propagation of perturbation from the impact site to the jet is still unclear (Valtonen et al 2017). Therefore, the post-effect of black hole-disc impaction could be a possibility for the X-ray outburst and this scenario may not be completely ruled out.…”