Primary black hole spin in OJ287 as determined by the General Relativity centenary flare

TL;DR

This paper confirms the binary black hole model of OJ287 through a 2015 outburst, accurately measuring the primary black hole's spin and testing general relativity predictions with high precision.

Contribution

It provides a precise measurement of the primary black hole's spin in OJ287 using the 2015 outburst, supporting general relativity and opening avenues for testing the no-hair theorem.

Findings

Outburst occurred as predicted, confirming the binary black hole model.

Measured black hole spin: chi = 0.313 +- 0.01.

Confirmed gravitational radiation loss at 2% accuracy.

Abstract

OJ287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts which are predictable in a binary black hole model. The model predicted a major optical outburst in December 2015. We found that the outburst did occur within the expected time range, peaking on 2015 December 5 at magnitude 12.9 in the optical R-band. Based on Swift/XRT satellite measurements and optical polarization data, we find that it included a major thermal component. Its timing provides an accurate estimate for the spin of the primary black hole, chi = 0.313 +- 0.01. The present outburst also confirms the established general relativistic properties of the system such as the loss of orbital energy to gravitational radiation at the 2 % accuracy level and it opens up the possibility of testing the black hole no-hair theorem with a 10 % accuracy during the present decade.