The NANOGrav 11-year Data Set: High-precision timing of 45 Millisecond Pulsars

TL;DR

This paper presents high-precision timing data over 11 years for 45 millisecond pulsars, aiming to detect low-frequency gravitational waves, and introduces new methods for data processing and noise modeling.

Contribution

It provides comprehensive timing solutions, new parallax and Shapiro delay measurements, and advanced noise characterization techniques for millisecond pulsars.

Findings

11 pulsars exhibit significant red noise

New parallax and Shapiro delay measurements obtained

Noise spectral indices are smaller than in non-recycled pulsars

Abstract

We present high-precision timing data over time spans of up to 11 years for 45 millisecond pulsars observed as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project, aimed at detecting and characterizing low-frequency gravitational waves. The pulsars were observed with the Arecibo Observatory and/or the Green Bank Telescope at frequencies ranging from 327 MHz to 2.3 GHz. Most pulsars were observed with approximately monthly cadence, with six high--timing-precision pulsars observed weekly, and all were observed at widely separated frequencies at each observing epoch in order to fit for time-variable dispersion delays. We describe our methods for data processing, time-of-arrival (TOA) calculation, and the implementation of a new, automated method for removing outlier TOAs. We fit a timing model for each pulsar that includes spin, astrometric, and, if necessary, binary parameters, in addition to time-variable dispersion delays and parameters that quantify pulse-profile evolution with frequency. The new timing solutions provide three new parallax measurements, two new Shapiro delay measurements, and two new measurements of large orbital-period variations. We fit models that characterize sources of noise for each pulsar. We find that 11 pulsars show significant red noise, with generally smaller spectral indices than typically measured for non-recycled pulsars, possibly suggesting a different origin. Future papers will use these data to constrain or detect the signatures of gravitational-wave signals.