The NANOGrav 15 year data-set: Customized chromatic noise models

​In June 2023, the North American Nanohertz Observatory for Gravitational waves (NANOGrav) reported strong evidence for the presence of a stochastic gravitational wave background (GWB) in our 15-year data set. While this is an important measurement, the recovered spectrum of the GWB remains very noise model dependent. This work revisits the NANOGrav results using customized chromatic noise models for all 67 pulsars in the data set. These new models utilize Gaussian Processes to account for radio frequency-dependent time delays to pulsar signals, including dispersion measure effects and scattering, while also including a global solar wind model. This study further investigates what affects these new noise models have on the GWB significance, parameter estimation, and spectral properties.