Elementary Wideband Timing of Radio Pulsars

Abstract

We present an algorithm for the simultaneous measurement of a pulse time-of-arrival (TOA) and dispersion measure (DM) from folded wideband pulsar data. We extend the prescription from Taylor (1992) to accommodate a general two-dimensional template "portrait", the alignment of which can be used to measure a pulse phase and DM. We show that there is a dedispersion reference frequency that removes the covariance between these two quantities, and note that the recovered pulse profile scaling amplitudes can provide useful information. We experiment with pulse modeling by using a Gaussian-component scheme that allows for independent component evolution with frequency, a "fiducial component", and the inclusion of scattering. We showcase the algorithm using our publicly available code on three years of wideband data from the bright millisecond pulsar J1824-2452A (M28A) from the Green Bank Telescope, and a suite of Monte Carlo analyses validates the algorithm. By using a simple model portrait of M28A we obtain DM trends comparable to those measured by more standard methods, with improved TOA and DM precisions by factors of a few. Measurements from our algorithm will yield precisions at least as good as those from traditional techniques, but is prone to fewer systematic effects and is without ad hoc parameters. A broad application of this new method for dispersion measure tracking with modern large-bandwidth observing systems should improve the timing residuals for pulsar timing array experiments, like the North American Nanohertz Observatory for Gravitational Waves.