Maxwell A. Fine
(he/him)

Hunting for Fast Radio Bursts (FRBs) with SWIFT/BAT

Advisors:
Prof. Ziggy Pleunis, and Prof. Jason Hessels

Fast Radio Bursts (FRBs) are highly energetic, micro-to-millisecond duration radio transients that are extragalactic in origin. Most observed FRBs are apparently non-repeating, while some ∼ 3% are known to repeat (CHIME/FRB Collaboration et al., 2023). Their progenitor(s) and emission mechanism(s) are areas of active debate; however, the primary theoretical source(s) for FRBs are compact objects such as neutron stars and magnetars – see Petroff et al. (2022) for a review on FRBs. Proposed FRB emission mechanisms fall into two broad categories: one where the emission originates close to the compact object (Rs ≲ 10⁷cm), inside of the magnetosphere, and another where the emission is released at larger distances (Rs ≳ 10⁹cm) (Kumar et al., 2024). Until recently, observations were not able to distinguish between the two emission models. Kumar et al. (2024) proposed a scintillation analysis technique to distinguish between the two emission mechanisms based on their scintillation properties imprinted by their host Galaxies. Similar techniques have been used for compact radio sources such as the Crab pulsar, and for Gamma-Ray Burst (GRB) afterglows (Main et al., 2021; Lin et al., 2023; Frail et al., 1997).

Scintillation is one probe that astronomers use to study structures along the line-of-sight of FRBs. Diffractive scintillation arises from interference caused by multipath propagation of radio waves through inhomogeneous plasma. This leads to frequency-dependent and time-dependent stochastic variations in the FRB spectrum. Scintillation is characterized by the decorrelation bandwidth, ∆ν_DC, which is approximately given by the relation ∆ν_DC ∼ k²τ_s, where τ_s is the scattering timescale. Here, k is a constant with a value ranging typically from 1 to 2. The decorrelation bandwidth is inversely proportional to the scattering timescale, and it follows the relation ∆ν_DC ∝ να, with α ∼ 4. However, not all FRBs show measurable scintillation from their host galaxy, and its analysis requires high-resolution data in both frequency and time, which has not always been recorded. Additionally, the bursts must be sufficiently bright for the analysis, and the analysis must account for instrumental effects as well as scintillation from the Milky Way (Cordes & Lazio, 2002).

Nimmo et al. (2024) used scintillation measurements to constrain the size of the emission region for (an apparently one-off) FRB 20221022A; their conclusions support a magnetosphere origin. Time-variability of scintillation for repeating FRBs has recently started to be studied as well (see Wu et al., 2024a,b). Time-variability of scintillation studies has been done for Pulsars to study their local environments (Cordes et al., 2006).

This project will focus on repeating FRBs observed with the Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB). Repeaters have an advantage, as it should be possible to stack bursts from a repeating FRB source if the bursts are within the scintillation timescale. This would increase their signal-to-noise. Another advantage is the possibility to study the time-variability of their scintillation. Repeaters are further interesting as they might be from a different population(s) than one-off FRBs. CHIME is a radio interferometer with no moving parts, and its wide field-of-view, ∼ 200 square degrees, makes it excellent for detecting FRBs (CHIME/FRB Collaboration et al., 2018).

For this project, I will be joining the CHIME/FRB collaboration and Astroflash research groups. The objective is to leverage CHIME/FRB’s large catalog of repeating FRBs to conduct a similar scintillation analysis for repeating FRBs to study not only their local environments, but also the time-variability of their local environments.

Utilizing the 25m Dwingeloo Radio Telescope (DRT) to Study Fast Radio Bursts (FRBs) at ASTRON, the Netherlands 🇳🇱 📡

Advisors:
rofessor Jason Hessels, and Dr. Tammo Jan Dijkema

Over summer of 2024 I worked at Astron Institue for Radio Astronomy, in the Netherlands as a Summer Research Fellow utilizing the historic 25m Dwingeloo Radio Telescope (DRT). The project was supervised by Professor Jason Hessels and Dr. Tammo Jan Dijkema. The DRT was the largest radio telescope in the world when it was built in 1956; today it is a museum and national monument in the Netherlands and is operated by volunteers who give public tours. Recently, there has been interest in using "small" 25m-35m radio telescopes for high cadence FRB observations.

For the project, I became a volunteer and developed a real-time detection pipeline for repeating FRBs. The highlight of this project was detecting a burst from FRB20240619D, which showcases the DRT's enduring scientific capability. The results will contribute to an upcoming paper, and the DRT will be used in future FRB observation campaigns.

Hunting for Fast Radio Bursts (FRBs) with SWIFT/BAT

Advisors:
Dr. Paul Schols, and Dr.Ziggy Pleunis

I started this as a summer research project over the summer of 2022, and then continued this as my AST425 project (Year long Thesis Course) at UofT. Image Credit NASA.

Thesis Abstract:
Fast radio bursts (FRBs) are brief radio pulses with unknown extragalactic origins. So far FRBs have only been detected at radio frequencies. Several FRB progenitor models propose that these bursts originate from magnetars, and predict associated γ-ray emission. Previous γ-ray searches have only examined two repeating FRB sources. This study used data from the Swift/BAT telescope which was obtained with GUANO to analyze 380 CHIME/FRB targets. I made an analysis pipeline that estimates the peak Signal-To-Noise Ratio (S/N) for each target, and determines fluence limits. I used seven energy bands ranging from 10-350 keV for S/N and 10-150 keV for fluence, 13 timescales from 0.01 to 6 seconds and 6 spectrum models. I used a search window of 6 s around the FRB observation in radio wavelengths. S/N estimates were determined for 244 sources analyzed, no FRBs were detected. Fluence limits were determined for 49 FRBs at a level of ∼ 10−7 ergs cm−2 in the 10-150 keV band (95% confidence). It is possible that nearby FRBs could be detected by Swift/BAT, and future research will focus on addressing issues that led to failures in the analysis of targets and analyzing a larger CHIME/FRB catalog.

AST425 Midway Presentation
AST425 Final Presentation
AST425 Final Thesis

Gravitational Waves from Magnetar Giant Flares

Advisors:
Dr. Sarah Gossan, and Prof. Bryan Gaensler

This was my project for PHYD01 (Semester Long Thesis Course) at UofT. Image Credit NASA.

Thesis Abstract:
The goals of this study were to improve our understanding of gravitational waves from magnetar giant flares, and to determine if third generation gravitational wave detectors will be able to detect magnetar giant flares. In order to test this, I implemented simplistic emission waveforms, using parameters based on the known magnetar giant flares. I then used these waveforms to estimate the signal-to-noise ratio for third generation detectors. My resulting highest signal-to-noise was $\sim 10^{-3}$ which is four orders of magnitude smaller then my detection threshold of 8, indicating that third generation detectors will be unable to detect magnetar giant flares.

Final Presentation

Developing Robust Error Analysis for Radio Polarization Surveys

Advisors:
Dr. Cameron L. Van Eck, and Prof. Bryan Gaensler

I started this as a summer research project over the summer of 2021 at UofT. Image Credit ASKAP. For this project, which was partially funded by a grant awarded to me from the Canadian Institute for Theoretical Astrophysics (CITA), focused on error testing an error analysis pipeline for POSSUM. I found that one of the estimated errors was too small, and implemented a correction.

Project Abstract:
The "Polarization Sky Survey of the Universe's Magnetism" (POSSUM) is one of the eight major surveys to be conducted by the Australian Square Kilometer Array Pathfinder (ASKAP). POSSUM will make a catalogue of Faraday rotation measures (RMs) for around a million extragalactic radio sources – that's an increase of 20x the current known Faraday rotation measures (RMs). The goal of this project was to develop a robust error analysis of the POSSUM data as a part of the POSSUM data pipeline.
The key result from this project was the discovery that the output error bars from the pipeline are slightly too small. If the error bars were the correct size, then in the histogram below would match the Gaussian distribution exactly. However, the normalized residual is too wide for the Gaussian - this means the error bars are too small. Having too small errors for the pipeline is a concern as future research will depend on the accuracy of the errors.

POSSUM Presentation

Hunting for Radio Sources in Extreme Magnetized Environments

Advisors:
Dr. Cameron L. Van Eck, and Prof. Bryan Gaensler

I started this as a summer research project in 2020 at UofT, and continued it for another year or so. For the first project, I contributed to improving the RM synthesis algorithm for cases of extreme bandwidth depolarization, with the results integrated into the RM-Tools package. This project was motivated by the recent discovery of extreme bandwidth depolarized sources, where the traditional RM synthesis algorithm was no longer adequate. This lead to the publication of Maxwell A. Fine , Cameron L. Van Eck, & Luke Pratley “Correcting Bandwidth Depolarization by Extreme Faraday Rotation”, Monthly Notices of the Royal Astronomical Society 2022, submitted.

Paper Abstract: Measurements of the polarization of radio emission are subject to a number of depolarization effects such as bandwidth depolarization, which is caused by the averaging effect of a finite channel bandwidth combined with the frequency-dependent polarization caused by Faraday rotation. There have been very few mathematical treatments of bandwidth depolarization, especially in the context of the rotation measure (RM) synthesis method for analyzing radio polarization data. We have found a simple equation for predicting if bandwidth depolarization is significant for a given observational configuration. We have derived and tested three methods of modifying RM synthesis to correct for bandwidth depolarization. From these tests we have developed a new algorithm that can detect bandwidth-depolarized signals with higher signal-to-noise than conventional RM synthesis and recover the correct source polarization properties (RM and polarized intensity). We have verified that this algorithm works as expected with real data from the LOFAR Two-metre Sky Survey. To make this algorithm available to the community, we have added it as a new tool in the RM-Tools polarization analysis package.

End of SURP Poster