Long Term (250 years) Hydrodynamical Simulation of the Supermassive Black Hole Binary OJ287

TL;DR

This study uses 3D hydrodynamic simulations to model the long-term behavior of the SMBH binary OJ287, revealing impacts on accretion rates and variability patterns that inform future gravitational wave and observational studies.

Contribution

It presents the first detailed hydrodynamic simulation of OJ287's SMBH binary, demonstrating how binary dynamics influence accretion variability and potential observational signatures.

Findings

Simulation with realistic mass ratio matches current OJ287 models.

Secondary impacts cause 10-20% increases in accretion rate.

Quasi-periodic impact timing aligns with observed variability.

Abstract

With upcoming facilities capable of detecting photometric and gravitational wave signals from supermassive black hole (SMBH) binaries, studying their long-term accretion-driven variability is timely. OJ287 is a bright, nearby ($z=0.3$), and well-studied candidate for a SMBH binary. As such, it is an excellent case study for how binary dynamics could influence observed active galactic nucleus (AGN) photometric variability. We present 3D hydrodynamic simulations of OJ287, using the code PHANTOM. We simulate two mass ratios: (i) M$_1$ $=$ 1.835$\times$10$^{10}$ M$_\odot$ with M$_2$ $=$ 1.4$\times$10$^{8}$ M$_\odot$, (ii) M$_1\approx$ M$_2$ ($\sim10^{8}$ M$_\odot$) along and (iii) control of a single SMBH and accretion disc. We find that the simulation with masses 1.835$\times$10$^{10}$ M$_\odot$ and 1.4$\times$10$^{8}$ M$_\odot$ evolves consistently with the most currently accepted model of OJ287 as a precessing SMBH binary. The secondary's impacts with the disc result in the formation of spiral density waves and a corresponding $\sim$10-20% increases in the mass accretion rate of the primary SMBH. The impact timings and the mass accretion rate spikes show quasi-periodic variability as a result of the precession of the secondary's orbit with intervals between impacts ranging from $\sim$ 1 year to $\sim$ 10 years. In the near-equal mass case, the disc of the primary becomes tidally disrupted after $\sim$ 2 years. Consequently, the near-equal mass system with a period of 12 years is not a viable candidate for OJ287. This modeling provides insights into the potential signatures of SMBH binaries by both gravitational wave observatories and the Rubin Legacy Survey of Space and Time.