Testing the accuracy of time-delay models for Continuous Gravitational Wave searches

Continuous Gravitational Waves (CW) are quasi-monochromatic, persistent signals embedded within the data observed by ground-based gravitational wave detectors. Despite extensive searches, no detections have been made to date, highlighting the need for meticulous examination of every step in the search methodology.

In this study, we focus on one critical aspect: computing the time-delays. The motion of the Earth introduces Doppler modulation to a CW signal. To demodulate the signal, the reference frame is shifted from the detector frame to the Solar System Barycenter (SSB) frame. Central to this process is the time delay, which quantifies the difference in arrival times of the signal at the SSB compared to the ground-based detector.

We use LALSuite, a gravitational-wave-data analysis software, to compute the time delays. To assess their accuracy, we compare them against those from PINT, a relatively-recent pulsar timing software commonly used to provide precise timing solutions. Notably, this is the first comparison of its kind for neutron stars in binary systems.

Our results demonstrate that LALSuite achieves a high level of accuracy (within 5 micro-seconds) when benchmarked against PINT, improving confidence that potential CW signals are not being missed due to inaccuracies in time-delay modeling. These findings reinforce the reliability of current CW search methodologies.