Measuring Black Hole Spin in OJ287
  We model the binary black hole system OJ287 as a spinning primary and a
non-spinning secondary. It is assumed that the primary has an accretion disk
which is impacted by the secondary at specific times. These times are
identified as major outbursts in the light curve of OJ287. This identification
allows an exact solution of the orbit, with very tight error limits. Nine
outbursts from both the historical photographic records as well as from recent
photometric measurements have been used as fixed points of the solution: 1913,
1947, 1957, 1973, 1983, 1984, 1995, 2005 and 2007 outbursts. This allows the
determination of eight parameters of the orbit. Most interesting of these are
the primary mass of $1.84\cdot 10^{10} M_\odot$, the secondary mass $1.46\cdot
10^{8} M_\odot$, major axis precession rate $39^\circ.1$ per period, and the
eccentricity of the orbit 0.70. The dimensionless spin parameter is
$0.28\:\pm\:0.01$ (1 sigma). The last parameter will be more tightly
constrained in 2015 when the next outburst is due. The outburst should begin on
15 December 2015 if the spin value is in the middle of this range, on 3 January
2016 if the spin is 0.25, and on 26 November 2015 if the spin is 0.31. We have
also tested the possibility that the quadrupole term in the Post Newtonian
equations of motion does not exactly follow Einstein's theory: a parameter $q$
is introduced as one of the 8 parameters. Its value is within 30% (1 sigma) of
the Einstein's value $q = 1$. This supports the $no-hair theorem$ of black
holes within the achievable precision. We have also measured the loss of
orbital energy due to gravitational waves. The loss rate is found to agree with
Einstein's value with the accuracy of 2% (1 sigma).
