Abstract
Wideband timing of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) datasets, where a single time-of-arrival (TOA) and a single dispersion measure (DM) are measured using the entire bandwidth of each observation, was first done for the 12.5-year dataset, and proved to be invaluable for characterizing the time-varying dispersion measure, reducing the data volume, and for improving the overall timing precision. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) Telescope has been observing most NANOGrav millisecond pulsars (MSPs) at nearly daily cadence (compared to roughly monthly cadence for other NANOGrav observations) since 2019 with the objective of integration into future pulsar timing array (PTA) datasets. In this paper, we show the results of integration of high-cadence, low-observing-frequency CHIME data with data from the NANOGrav experiment for an isolated MSP PSR~J0645 $+$ 5158 and three binary MSPs PSR~J1012 $+$ 5307, PSR~J2145 $-$ 0750, and PSR~J2302 $+$ 4442. Using a wideband timing pipeline which we also describe, we present updated timing results for all four sources, including improvements in measurements of relativistic post-Keplerian parameters for the three binary pulsars in this analysis. For PSR~J2302 $+$ 4442, we report an updated strong detection of Shapiro delay from which we measured a companion mass of$0.35^{+0.05}_{-0.04}\ M_{\odot}$ , a pulsar mass of$1.8^{+0.3}_{-0.3}\ M_{\odot}$ , and an orbital inclination of${80^{\circ}}^{+1}_{-2}$ . We also report updated constraints on the reflex motion for PSR~J2145 $-$ 0750 using a combination of Very Long Baseline Array astrometry and our updated measurement of the time derivative of the projected semi-major axis of the pulsar orbit as a prior.