The NANOGrav 15yr dataset: Customized Chromatic Noise Models

In 2023, NANOGrav, alongside pulsar timing arrays around the world, reported strong evidence for a stochastic gravitational wave background (GWB). The spectral characterization of this emerging background remains noise model dependent. Dispersion delays in the interstellar medium and interplanetary medium are chromatic (radio-frequency dependent) noise sources which together can be up to 2 orders of magnitude louder than the GWB. In order to better characterize the GWB, we construct multiple sets of customized chromatic noise models for all of the pulsars in the NANOGrav 15yr dataset. We test the significance of multiple noise models for each pulsar and report results which demonstrate the impact of customized chromatic noise models on GWB parameter estimation and significance.