P o S ( T e x a s 2 0 1 0 ) 0 4 3 Searching for a pulsar black hole binary

For tests of General Relativity (GR) and alternative theori s of gravity nature has provided perfect “laboratories” in the form of relativistic binary pulsars: pulsars (highly magnetized rapidly rotating neutron stars) orbiting in compact binary systems with e it er a second neutron star or a white dwarf. In such systems the effects predicted by GR, and some a ltern tive theories of gravity, are significant because of the extreme gravitational fields pres ent. Precise radio timing measurements of the binary pulsar, PSR B1913+16 provided the first evidenc e for the existence of gravitational waves (GWs) [1]. Since then, the highly relativistic Double P ulsar system, with an orbital period of just 2.4 hours, has provided the most precise test of GR in t he so-called “strong field” regime, agreeing with the theory to a level of 0.05 per cent [2]. Howev er, the Double Pulsar is by no means the most extreme binary pulsar system we may expect to fi nd e.g. [3].