A Realistic Pulsar - Supermassive Black Hole Timing Model

TL;DR

This paper develops a detailed pulsar timing model around a supermassive black hole, incorporating advanced effects and proper motion, to enhance tests of gravity near Sagittarius A* with future radio telescope observations.

Contribution

It introduces the first realistic pulsar-SMBH timing model that includes next-to-leading order light delays and proper motion effects, improving parameter measurement accuracy.

Findings

Forecasts high-precision measurements of Sgr A* parameters.

Incorporates proper motion effects to resolve spin degeneracies.

Provides a practical tool for future pulsar-SMBH system analysis.

Abstract

Timing observation of pulsars orbiting around a supermassive black hole (SMBH) can measure the spacetime around the SMBH to a high precision and thus be a novel probe of the gravity theory. Future high-frequency surveys of the Galactic Centre (GC) region to be performed by the next-generation radio telescopes, such as the SKA, may discover pulsars that orbit around Sagittarius A* (Sgr A*), the SMBH dwelling in our GC. In this paper, we present a realistic pulsar-SMBH timing model based on the post-Newtonian equations of motion of the pulsar. Considering the expected timing precision in the future, we take into account several next-to-leading order light propagation time delays in the timing model. For the first time, we include the effects of proper motion of Sgr A*, which were expected to break the spin measurement degeneracy. We forecast the measurement precision of various parameters of Sgr A*, and discuss the data analysis procedure in the presence of red noise, which can be strong if the pulsar is a normal pulsar. The realistic timing model constructed in this study will serve as a useful tool in future searching and timing of pulsar-SMBH systems in the GC.