Timing observations of the 8 hour binary pulsar 2127+11C in the globular cluster M15

We present new results on the position and characteristics of the 8 hr binary pulsar 2127+11C in the postcore-collapse (PCC) globular cluster M15. Our results indicate that PSR 2127+11C has been ejected from the cluster core via a close encounter with another binary system or isolated star. In particular, the position derived from a phase-connected timing solution places the PSR 2127+11C system 2.7 pc (projected) from the core, well outside the compact region containing the other four detected pulsars and the X-ray binary system X2127+11/AC 211. While PSR 2127+11C is likely still bound to the cluster, it is nonetheless probable that other compact binary pulsars have been totally ejected, thereby contributing to the population of field binary pulsars. Timing results from PSR 2127+11C also show a relativistic advance of periastron of 4°.46 yr^-1, indicating that the total mass of the system is 2.71 M_⊙.