Black Hole-Pulsar Binary Tests of Gravity*

Binary pulsars allow precision tests of gravity and have placed stringent bounds on a broad class of theories beyond general relativity. Radio telescopes such as FAST and SKA may discover a pulsar orbiting a black hole in the future. In this talk, we examine the prospects of testing alternative theories of gravity with these black hole-pulsar binaries. In particular, we focus on tests using the orbital decay rate post-Keplerian parameter. We examine gravity with a varying gravitational constant and massive Brans-Dicke theory.  Constraints are placed through the simulated measurement accuracy of the orbital decay rate for black hole-pulsar binaries with FAST/SKA. We find that one can constrain the amount of time variation in Newton’s constant G to be slightly weaker than the current strongest bound from solar system experiments, though the former bounds are complementary to the latter since they probe different regime of gravity. Furthermore, we find that a black hole-pulsar binary more strongly constrains the massive Brans-Dicke parameter space, particularly in the low mass sector. These results show that a black hole-pulsar binary allow for more precise tests of gravity.