We report the direct measurement of orbital period decay in the double neutron star pulsar system PSR B2127+11C in the globular cluster M15 at the rate of ( -3.95 \pm 0.13 ) \times 10 ^ { -12 } , consistent with the prediction of general relativity at the \sim 3 \% level .
We find the pulsar mass to be m _ { p } = ( 1.358 \pm 0.010 ) M _ { \odot } and the companion mass m _ { c } = ( 1.354 \pm 0.010 ) M _ { \odot } .
We also report long-term pulse timing results for the pulsars PSR B2127+11A and PSR B2127+11B , including confirmation of the cluster proper motion .