Author ORCID Identifier

https://orcid.org/0000-0002-2972-522X

Semester

Spring

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Maura McLaughlin

Committee Member

Sarah Burke Spolaor

Committee Member

Paul Cassak

Committee Member

Julia Deneva

Abstract

Radio pulsars are highly magnetized, rapidly rotating neutron stars which emit beams of radio waves from their magnetic poles. Their incredible rotational stability allows for their use in a variety of high-energy astrophysical studies, though the details of their internal structure and emission mechanisms are still unknown. We use observations of a cross-section of the pulsar population in order to investigate the nature of their evolution, their emission properties, and their environments.

First we derive timing solutions for three pulsars discovered through their sporadic single pulses. It was possible to obtain timing solutions through a set of single-pulse times of arrival (TOAs) in addition to a set of TOAs from summing their emission in time. This allows us to compare each timing solution's derived physical parameters, finding that they agree within two standard deviations with similar error bar sizes. We find significant degrees of pulse clustering in the wait time distributions of each pulsar, and the presence of low-level emission outside the bright pulses indicates that these sources are dim radio pulsars, as opposed to extremely transient sources.

We then present the timing solutions and multi-wavelength followup of four millisecond pulsars discovered by the Arecibo 327-MHz Drift-scan Survey. Three of these pulsars are in binary systems, consisting of a redback (PSR J2055+1545), a black widow (PSR J1630+3550), and a neutron star--white dwarf binary (PSR J2116+1345). PSRs J2055+1545 and J2116+1345 are colocated with unidentified Fermi-LAT gamma-ray sources, and with our radio timing solution, we use the Fermi data to detect gamma-ray pulsations and extend the timing solution for PSR J2116+1345 over 14 years. The extreme orbital variability of the redback currently precludes the detection of a gamma-ray pulse profile, though the spatial colocation and pulsar-like spectral and temporal properties of the source make the association convincing. The optical counterpart to PSR J2055+1545 was detected in three surveys, and later optical spectroscopy confirmed our characterization of a late G-type star mildly irradiated by the pulsar wind.

Finally, we report on multi-hour radio observations of the fastest-spinning magnetar \textit{Swift} J1818.0--1607 at six different frequencies, between six and nine months post-outburst. This magnetar may represent an evolutionary link between rotation-powered pulsars and magnetars, and we use these observations to study the evolution of its pulse profile morphology, spectrum, and single-pulse properties in frequency and time. We find evidence of a spectral peak at 5.4 GHz, which we model as thermal free-free absorption by the ionized material surrounding the magnetar. The average pulse profile is remarkably stable across all of our observations, which suggests the configuration of the magnetosphere settled into a more stable state post-outburst.

Download

Share

COinS