ngVLA Key Science Goal 4: Fundamental Physics with Galactic Center Pulsars

Pulsars in the Galactic Center (GC) are important probes of General Relativity, star formation, stellar dynamics, stellar evolution, the interstellar medium, and the supermassive black hole accretion flow. In particular, a pulsar in orbit around the GC black hole, Sgr A*, will provide an unprecedented probe of black hole physics and General Relativity, measuring black hole mass, spin, and quadrupole moment, and testing the Kerr metric at sensitivities orders of magnitude better than any other method. The rich recent star formation history and abundant population of high mass stars indicate that thousands of pulsars should be present in the GC. After years of searching, however, only a small number of pulsars in the central tens of parsecs are known. Notable among these is the magnetar J1745-2900, only 0.1 pc in projection from Sgr A*, and the first pulsar found to orbit a supermassive black hole. This source has provided the community with an unprecedented tool for characterizing the environment and population of GC pulsars. Discovery of additional pulsars in even closer orbits is needed for our science goals. High-frequency observations are required to mitigate the strong interstellar scattering, and high sensitivity is required to overcome the typically steep pulsar spectra. The ngVLA will have nearly an order of magnitude more sensitivity than current telescopes in the 5–30 GHz range that is expected to be optimal for detection of both canonical and millisecond pulsars at the Galactic Center. The ngVLA is a design and development project of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.