A massive binary black-hole system in OJ287 and a test of general relativity

TL;DR

This paper reports a test of general relativity using a binary black-hole system in quasar OJ287, confirming gravitational wave emission effects consistent with Einstein's theory in a strong-field regime.

Contribution

It provides the first observational evidence of gravitational wave emission from a binary black-hole system in a quasar, testing strong-field predictions of general relativity.

Findings

Outburst timing matches predictions from the binary black-hole model

Evidence supports orbital energy loss due to gravitational waves

Results are consistent with general relativity within 10 percent

Abstract

Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton's theory. Binary pulsars provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ287. This quasar shows quasi-periodic optical outbursts at 12 yr intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system. In the absence of gravitational wave emission the outburst would have happened twenty days later.