Prospects for accurate distance measurements of pulsars with the SKA: enabling fundamental physics

TL;DR

The paper evaluates how the SKA can precisely measure pulsar distances via parallax, enabling tests of fundamental physics and interstellar medium studies, using simulations of two measurement methods.

Contribution

It compares two methods for pulsar parallax measurement with the SKA and estimates the number of pulsars measurable at specific accuracies and distances.

Findings

Method 1 can measure parallaxes up to 13 kpc for about 9,000 pulsars.

Method 2 can measure parallaxes for about 3,600 millisecond pulsars up to 9 kpc.

High-precision distance measurements will enhance tests of general relativity.

Abstract

Parallax measurements of pulsars allow for accurate measurements of the interstellar electron density and contribute to accurate tests of general relativity using binary systems. The Square Kilometre Array (SKA) will be an ideal instrument for measuring the parallax of pulsars, because it has a very high sensitivity, as well as baselines extending up to several thousands of kilometres. We performed simulations to estimate the number of pulsars for which the parallax can be measured with the SKA and the distance to which a parallax can be measured. We compare two different methods. The first method measures the parallax directly by utilising the long baselines of the SKA to form high angular resolution images. The second method uses the arrival times of the radio signals of pulsars to fit a transformation between time coordinates in the terrestrial frame and the comoving pulsar frame directly yielding the parallax. We find that with the first method a parallax with an accuracy of 20% or less can be measured up to a maximum distance of 13 kpc, which would include 9,000 pulsars. By timing pulsars with the most stable arrival times for the radio emission, parallaxes can be measured for about 3,600 millisecond pulsars up to a distance of 9 kpc with an accuracy of 20%.