Pulsar timing and the detection of black hole binary systems in globular clusters

The possible existence of intermediate mass binary black holes (IMBBHs) in globular clusters (GCs) offers a unique geometry in which to detect space-time oscillations. For certain pulsar-IMBBH configurations possible within a GC, the usual far-field plane wave approximation for the IMBBH metric perturbation severely underestimates the magnitude of the induced pulsar pulse time-of-arrival (TOA) fluctuations. In this letter, the expected TOA fluctuations induced by an IMBBH lying close to the line-of-sight between a pulsar and the Earth are calculated for the first time. For an IMBBH consisting of 10 Msolar and 10^3 Msolar components, a 10 year orbital period, and located 0.1 lyr from the Earth-Pulsar line of sight, the induced pulsar timing residual amplitude will be of order 5 to 500 ns.