Author ORCID Identifier

https://orcid.org/0000-0001-8057-0633

Semester

Fall

Date of Graduation

2024

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Sarah Burke-Spolaor

Committee Member

Duncan Lorimer

Committee Member

Maura McLaughlin

Committee Member

Ryan M. Shannon

Abstract

Fast radio transients are energetic bursts in centimeter or meter wave-lengths, lasting only milliseconds, and originating from both Galactic and extra-Galactic sources. In our Galaxy, these transients primarily originate from pulsars, which are rotating neutron stars. The more energetic extra-galactic transients, known as fast radio bursts (FRBs), have unknown origins. This thesis explores various techniques, including single dish and interferometric observations, to detect and accurately localize fast radio transients. It also investigates how the propagation effects of radio waves can reveal characteristics of the local environment and potential FRB sources. Furthermore, it demonstrates how FRBs can be used to study the medium between their source and the observer.

We report on observations of repeating FRB 20190520B over seventeen months, noting highly variable Faraday rotation that changes sign twice and shows depolarization below 1–3 GHz frequencies. These properties suggest changes in the parallel component of the integrated magnetic field along the line-of-sight, possibly due to a turbulent, magnetized plasma screen between 10-5 to 100 parsecs from the FRB source, potentially influenced by the winds of a binary companion.

Additionally, we detected radio bursts from the Galactic bulge using the realfast system at the Very Large Array during a survey of unidentified Fermi γ-ray sources, achieving subarcsecond localization. Follow-up observations with the Green Bank Telescope revealed more bursts, nearly 100% linearly polarized, with one showing up to 12% circular polarization. This high spatial resolution localization associates the source with the Fermi γ-ray source, suggesting it could be a young pulsar, magnetar, or binary pulsar system.

Finally, we report on the discovery and localization of two FRBs piercing M31 by the realfast fast transient detection system at the Very Large Array. The unique geometry of the line-of-sight of FRB 20230930A was used to constrain the electron density distribution of the M31. We localized FRB 20230930A to a host galaxy at a redshift z = 0.09. After accounting for the dispersion contribution from the Milky Way, the host galaxy and the intergalactic medium along the line-of-sight of FRB 20230930A, we estimate that M31 will likely contribute between 87–305 pc cm−3 with a 90% confidence. We also modelled out the M31’s disk contribution to the DM, which was determined to be 139 ±70 pc cm-3, to determine the halo contribution. We find that the halo of M31 will contribute between 28–219 pc cm-3 with 90% confidence. This is consistent with the predictions from modified Navarro-Frenk-White profile of M31 halo for a given impact parameter. The ions of the cool halo alone cannot account for the calculated DMM31,halo and therefore this measurement presents an indirect evidence of the hot halo of M31.

Download

Share

COinS