Dark Matter Constraints from the Eccentric Supermassive Black Hole Binary OJ 287

TL;DR

This paper uses the timing of electromagnetic flares from the binary black hole system OJ 287 to place constraints on the amount of dark matter near the primary black hole, testing predictions of general relativity.

Contribution

It provides the first constraint on dark matter spikes around supermassive black holes using observational data from a binary system.

Findings

Dark matter spike mass constrained to less than 3% of primary mass.

Timing of flares consistent with general relativity predictions.

Sensitive to dark matter distribution at 10-50 Schwarzschild radii.

Abstract

OJ 287 is a blazar thought to be a binary system containing a ~ 18 billion solar mass primary black hole accompanied by a ~ 150 million solar mass secondary black hole in an eccentric orbit, which triggers electromagnetic flares twice in every ~ 12 year orbital period when it traverses the accretion disk of the primary. The times of these emissions are consistent with the predictions of general relativity calculated to the 4.5th post-Newtonian order. The orbit of the secondary black hole samples the gravitational field at distances between O(10) and O(50) Schwarzschild radii around the primary, and hence is sensitive to the possible presence of a dark matter spike around it. We find that the agreement of general-relativistic calculations with the measured timings of flares from OJ 287 constrains the mass of such a spike to < 3% of the primary mass.