Wideband Observations of Radio Pulsars
Pennucci, Timothy, Astronomy - Graduate School of Arts and Sciences, University of Virginia
Ransom, Scott, As-Astronomy, University of Virginia
Demorest, Paul, National Radio Astronomy Observatory
Pulsars are exotic objects which have yielded a bounty of important astrophysical results. As rapidly rotating, highly magnetized neutron stars, pulsars' stable rotation and beamed radio emission enables their use as interstellar laboratory clocks. The extraordinary timing regularity of the millisecond pulsar (MSP) population permits some of the most precise measurements in astronomy. The discovery of MSPs raised the probability of directly detecting gravitational waves for the first time. Ongoing efforts by several pulsar timing array (PTA) collaborations compliment the ground- and space-based efforts of laser interferometers. One such PTA is the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). NANOGrav has recently employed a new set of wideband instruments to increase the sensitivity of their PTA, and the future of pulsar astronomy is moving towards progressively larger bandwidths. In this dissertation, we address the benefits and issues from adopting the new instrumentation, particularly for the scientific motivations of NANOGrav. We first develop a measurement technique for simultaneously obtaining pulse times-of-arrival (TOAs) and dispersion measures (DMs) using 2D models of evolving Gaussian components. We then apply the methodology broadly to a variety of pulsars, including a bright, test MSP in a globular cluster, the Galactic Center magnetar, and the entire suite of 37 MSPs from the NANOGrav 9-year data set. For a subset of these MSPs, we make targeted observations at specific orbital phases aimed at improving the timing models and constraining the Shapiro delay. With a few exceptions, we find positive or consistent timing results from the implementation of our first generation wideband timing protocol. Some highlights include: improved measurement uncertainties, mitigation of chromatic ISM effects, a reduction in the number of timing parameters and TOAs, signs of chromatic DMs, and at least one new pulsar mass.
PHD (Doctor of Philosophy)
pulsars, millisecond pulsars, pulsar timing, NANOGrav, Galactic Center magnetar
All rights reserved (no additional license for public reuse)