Noise Budget and Interstellar Medium Mitigation Advances in the NANOGrav Pulsar Timing Array

TL;DR

This paper discusses the comprehensive noise characterization in pulsar timing arrays, focusing on intrinsic pulsar noise and interstellar medium effects, to enhance gravitational wave detection capabilities.

Contribution

It provides a systematic evaluation of noise sources affecting pulsar timing arrays, including new insights into interstellar medium effects and future challenges with wideband observations.

Findings

Identification of key noise sources in pulsar timing data

Quantification of interstellar medium effects on timing precision

Preparedness for future wideband receiver challenges

Abstract

Gravitational wave (GW) detection with pulsar timing arrays (PTAs) requires accurate noise characterization. The noise of our Galactic-scale GW detector has been systematically evaluated by the Noise Budget and Interstellar Medium Mitigation working groups within the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. Intrinsically, individual radio millisecond pulsars (MSPs) used by NANOGrav can have some degree of achromatic red spin noise, as well as white noise due to pulse phase jitter. Along any given line-of-sight, the ionized interstellar medium contributes chromatic noise through dispersion measure (DM) variations, interstellar scintillation, and scattering. These effects contain both red and white components. In the future, with wideband receivers, the effects of frequency-dependent DM will become important. Having anticipated and measured these diverse sources of detector noise, the NANOGrav PTA remains well-poised to detect low-frequency GWs.