Choosing Suitable Noise Models for Nanohertz Gravitational-wave Astrophysics

Abstract

Accurately estimating the parameters of the nanohertz gravitational-wave background is essential for understanding its origin. The background is typically modeled with a power-law spectrum, parameterized with an amplitude A, which describes its intensity, and a spectral index γ, which describes how the background varies with frequency. Different collaborations have produced varied estimates of γ, some in tension with the value of γ = 13/3 expected for circular, gravitational-wave-driven binary black holes. However, estimates of A and γ can be affected by systematic errors and misspecified noise models. We investigate how systematic errors—which may plausibly be present in pulsar timing analy..