Kavli Affiliate: Lijing Shao
| First 5 Authors: Zexin Hu, Lijing Shao, , ,
| Summary:
As a key science project of the Square Kilometre Array (SKA), the discovery
and timing observations of radio pulsars in the Galactic Center would provide
high-precision measurements of the spacetime around the supermassive black
hole, Sagittarius A* (Sgr A*), and initiate novel tests of general relativity.
The spin of Sgr A* could be measured with a relative error of $lesssim 1%$ by
timing one pulsar with timing precision that is achievable for the SKA.
However, the real measurements depend on the discovery of a pulsar in a very
compact orbit, $P_blesssim0.5,{rm yr}$. Here for the first time we propose
and investigate the possibility of probing the spin of Sgr A* with two or more
pulsars that are in orbits with larger orbital periods, $P_bsim 2- 5,{rm
yr}$, which represents a more realistic situation from population estimates. We
develop a novel method for directly determining the spin of Sgr A* from the
timing observables of two pulsars and it can be readily extended for combining
more pulsars. With extensive mock data simulations, we show that combining a
second pulsar improves the spin measurement by $2-3$ orders of magnitude in
some situations, which is comparable to timing a pulsar in a very tight orbit.
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