Studying the Solar system dynamics using pulsar timing arrays and the LINIMOSS dynamical model

TL;DR

This study develops a precise dynamical model of the Solar system to assess how ephemeris uncertainties affect pulsar timing, revealing that inner planet perturbations are more significant than previously assumed, which impacts gravitational wave searches.

Contribution

The paper introduces LINIMOSS, a high-precision Solar system model, and analyzes the effects of ephemeris errors on pulsar timing, especially highlighting the importance of inner planet perturbations.

Findings

Outer planet effects are dominated by SSB shift.

Inner planet perturbations significantly affect Earth's orbit.

Complex residual spectra may cause false gravitational wave signals.

Abstract

Pulsar timing arrays (PTAs) can be used to study the Solar-system ephemeris (SSE), the errors of which can lead to correlated timing residuals and significantly contribute to the PTA noise budget. Most Solar-system studies with PTAs assume the dominance of the term from the shift of the Solar-system barycentre (SSB). However, it is unclear to which extent this approximation can be valid, since the perturbations on the planetary orbits may become important as data precision keeps increasing. To better understand the effects of SSE uncertainties on pulsar timing, we develop the LINIMOSS dynamical model of the Solar system, based on the SSE of Guangyu Li. Using the same input parameters as DE435, the calculated planetary positions by LINIMOSS are compatible with DE435 at centimetre level over a 20-year timespan, which is sufficiently precise for pulsar-timing applications. We utilize LINIMOSS to investigate the effects of SSE errors on pulsar timing in a fully dynamical way, by perturbing one SSE parameter per trial and examining the induced timing residuals. For the outer planets, the timing residuals are dominated by the SSB shift, as assumed in previous work. For the inner planets, the variations in the orbit of the Earth are more prominent, making previously adopted assumptions insufficient. The power spectra of the timing residuals have complex structures, which may introduce false signals in the search of gravitational waves. We also study how to infer the SSE parameters using PTAs, and calculate the accuracy of parameter estimation.