Statistical Analyses for NANOGrav 5-year Timing Residuals

TL;DR

This paper analyzes the statistical properties of pulsar timing residuals from NANOGrav's 5-year data to assess noise characteristics crucial for gravitational wave detection.

Contribution

It applies non-parametric tests to evaluate whiteness and Gaussianity of residuals, providing insights into noise behavior in pulsar timing data.

Findings

Most data are consistent with white noise

Many residuals deviate from Gaussianity, but outlier removal helps

Noise properties vary across different pulsars

Abstract

In pulsar timing, timing residuals are the differences between the observed times of arrival and the predictions from the timing model. A comprehensive timing model will produce featureless residuals, which are presumably composed of dominating noise and weak physical effects excluded from the timing model (e.g. gravitational waves). In order to apply the optimal statistical methods for detecting the weak gravitational wave signals, we need to know the statistical properties of the noise components in the residuals. In this paper we utilize a variety of non-parametric statistical tests to analyze the whiteness and Gaussianity of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 5-year timing data which are obtained from the Arecibo Observatory and the Green Bank Telescope from 2005 to 2010 (Demorest et al. 2013). We find that most of the data are consistent with white noise; Many data deviate from Gaussianity at different levels, nevertheless, removing outliers in some pulsars will mitigate the deviations.