Light propagation in the strong gravitational field of pulsar-black hole binary system
Abstract
Pulsar is the most accurate clock in our universe, the accuracy of its period is more than that of atomic clock. If pulse beams from pulsars pass through a black hole on their way to the Earth, they could be strongly deflected by the black hole. In principle, the received beams could be used as the probe for investigating the strong gravity near the event horizon of black hole. In this work, we investigate the effects of the strong gravity on the trajectory and time delay of pulse beams from a pulsar moving around the supermassive black hole (SMBH) which is believed to reside at the Galactic Center. Our results indicate that the trajectory and time delay sensitively depend on the observing angle. The larger the observing angle, the stronger the effects of the gravity. Compared to the gravitational mass of black hole, its spin has little effect on the trajectory and time delay of the pulse beams. If the observing angle is small, the effects of black hole spin can be neglected; therefore, future telescopes with high precision accuracy and sensitivity are needed to explore the effects of black hole spin.
