Physics & Astronomy ETDs

Publication Date

Fall 10-25-2023

Abstract

Pulsars are highly magnetized stellar remnants, among the densest known objects, and primarily produce radio emission in the form of lighthouse beams sweeping across the line of sight as a regular train of pulses. Apart from providing tests for matter in high-density regimes, general relativity, and plasma emission; perhaps the most notable characteristic is their applicability as precise astronomical clocks to measure various effects. Pulsar Timing Arrays (PTAs) are galactic scale detectors analogous to ground-based detectors of Gravitational Waves (GWs) like LIGO, with the aim of detecting low-frequency nano-Hz GWs from coalescing binary supermassive black holes. PTAs consist of a large number of millisecond pulsars, with continuous addition of new sources to the array and improvements to sensitivity.

Thus, this thesis is divided into two main aspects of pulsar astronomy: I) studying the fundamental properties of pulsars in the broader context of their emission and how they evolve with the observed frequency, II) and characterizing the propagation path through the interstellar medium (ISM). Geared towards these goals, we study a sample of 100 pulsars over a decade of low frequency observations along with a young pulsar at high frequency. We investigate the effect of inadequate solar wind modeling on pulsar timing measurements and suggest improvements to existing models to provide improved corrections. We also study the bow-shock pulsar wind nebula of pulsar J0002+6216, one of the fastest-moving pulsars at the time of its discovery, and evaluate these results in the broader context of pulsar-ISM interactions. Finally, we provide the largest catalog of pulsars detected at low frequencies while making the most sensitive measurements of inhomogeneities and turbulence in the ISM by studying pulsar dispersion and scattering over a decade. These measurements are then compared in the context of prior high frequency measurements to draw inferences on the nature of ISM inhomogeneities. We hope that this study will motivate future modeling of pulsar propagation through the ISM and improve the sensitivity of PTAs.

Degree Name

Physics

Level of Degree

Doctoral

Department Name

Physics & Astronomy

First Committee Member (Chair)

Greg B. Taylor

Second Committee Member

Kevin Stovall

Third Committee Member

Jayce Dowell

Fourth Committee Member

Frank Schinzel

Language

English

Keywords

Pulsars:general, ISM:general, PTAs, Frequency and Time Dependent Dispersion Measure, Polarization and Time Dependent Rotation Measure, Low-frequency Pulse Profile and Spectra

Document Type

Dissertation

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