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MAX-PLANCK-INSTITUT FÜR RADIOASTRONOMIE Targeted Fast Radio Burst Searches with the Effelsberg 100-m Radio Telescope Dissertation zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich–Wilhelms–Universität, Bonn vorgelegt von Guðjón Henning Hilmarsson aus Reykjavík, Island Bonn 2020 1. Referent: Prof. Dr. Michael Kramer 2. Referent: Prof. Dr. Norbert Langer Tag der Promotion: 26.2.2021 Erscheinungsjahr: 2021 Angefertigt mit Genehmigung der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich–Wilhelms–Universität Bonn Targeted Fast Radio Burst Searches with the Effelsberg 100-m Radio Telescope Abstract by G. Henning Hilmarsson for the degree of Doctor rerum naturalium Fast radio bursts (FRBs) are bright, energetic, millisecond duration radio bursts of extragalactic origin. The source of FRBs still remains an open problem. Since the discovery of FRBs in 2007, over 100 FRBs have been detected. Most FRBs are single-burst events, while others are observed to be repeating sources. Due to their cosmological origin, FRBs can be used as probes of the intergalactic medium and the medium of their host galaxies. Roughly ten FRBs have been localised to a host galaxy. Of those, FRB121102 was both the first discovered repeating FRB and the first FRB localised to a host galaxy, and was the primary motivation for the vast majority of the observations performed in this thesis. The FRB121102 bursting source has been proposed to originate from a magnetar within a supernova remnant (SNR), a scenario that can account for repeating bursts, an associated persistent radio source (PRS), and large Faraday rotation measures (RMs). Large, single-dish telescopes have high sensitivities and small fields of view, making them ideal for targeted and follow-up surveys. This thesis focuses on targeted FRB searches with single-dish telescopes, with the Effelsberg 100-m ra- dio telescope at the forefront. The surveys in this thesis were performed in order to obtain a better understanding of the origin of FRBs, specifically repeating ones, by observing known FRBs and potential hosts of FRB sources, with each scientific chapter being a different approach to that goal. The commissioning of a phased array feed (PAF) receiver at Effelsberg is presented in Chapter3. With PAFs, highly customisable beams can be formed on the sky, providing more flexibility than typical multi-beam receivers while also having a larger field of view. PAFs and their use cases are introduced, along with a detailed discussion on the Effelsberg PAF observations at 1.4 GHz. The main observing targets were PRSs associated with galactic disks or star formation regions to search for FRB121102-like bursting sources, and other FRBs such as two of the repeating FRBs, FRB121102 and FRB180814.J0422+73. No bursts were detected, so upper limits (ULs) to the burst rates were calculated based on the observations. The burst rate of FRB121102 was also scaled to each PRS. The scaled rates of five of the eleven PRSs were constrained by the UL rates at the 95% confidence level (CL), rejecting the hypothesis of an FRB121102-like source associated with those PRSs. Chapter4 presents the observations of ten superluminous supernovae (SLSNe) and long gamma-ray bursts (LGRBs) with Effelsberg using the S45-mm receiver at 5.3–9.3 GHz. SLSNe and LGRBs were targeted due to the similarities be- tween their host galaxies and the host galaxy of FRB121102, and were therefore observed to search for FRB121102-like sources. As no bursts were detected, UL burst rates and scaled FRB121102 rates to each target were calculated. None of the scaled rates were constrained by the ULs at the 95% CL. Furthermore, a PRS concident with the SLSN PTF10hgi was added as a target and observed with the PAF at Effelsberg and the ultra-wideband-low (UWL) receiver at the Parkes 64-m radio telescope in Australia. The FRB121102 rate scaled to PTF10hgi was excluded at the 99% CL. The apparent clustering of bursts from FRB121102 can be explained with a Weibull distribution. For such a distribution, a non-detection probability of 14% and 16% was calculated for the PAF and UWL observations, respectively. Chapter5 investigates the temporal RM evolution of FRB121102. Faraday rotation is the rotation of the linearly polarised plane of a signal induced by the line of sight magnetic field. The rate of this rotation across frequency is quantified by the RM. The first RM measurements of FRB121102 was exceptionally high, 1:46 × 105 rad m−2 in the source reference frame, decreasing down to 1:33 × 105 rad m−2 in seven months. In Chapter5, sixteen additional FRB121102 RM measurements are presented from burst detections with the Arecibo 305-m radio telescope, the Effelsberg 100-m radio telescope, and the Karl G. Jansky Very Large Array, showing a continued decreasing trend in RM over time down to 9:7× 104 rad m−2 at the most recent epoch of August 2019. Erratic, short-term RM variations of ∼ 103 rad m−2 per week were seen from multiple detections within a 30-day window. The complete RM sample of FRB121102, spanning 2.5 years, was compared to theoretical RM evolution models of magnetars within SNRs. The data were inconsistent with model varieties where the remnant magnetar is surrounded by a constant density interstellar medium. However, the data agree with model varieties where the magnetar is surrounded by a magnetar wind nebula. The age of the FRB121102 bursting source was also estimated based on the RM evolution models and was found to be 6–17 years old at the time of the first FRB121102 RM measurement (at the end of 2016). The RM evolution of FRB121102 is also compared to the Galactic center magnetar, PSR J1745-2900, which has shown a similarly drastic decrease in its absolute RM over time. To the good people and animals in my life “When you do things right, people won’t be sure you’ve done anything at all.” God Futurama, S3E20 “One of the major difficulties Trillian experienced in her relationship with Zaphod was learning to distinguish between him pretending to be stupid just to get people off their guard, pretending to be stupid because he couldn’t be bothered to think and wanted someone else to do it for him, pretending to be outrageously stupid to hide the fact that he actually didn’t understand what was going on, and really being genuinely stupid. He was renowned for being amazingly clever and quite clearly was so - but not all the time, which obviously worried him, hence, the act. He preferred people to be puzzled rather than contemptuous” Douglas Adams The Hitchhiker’s Guide to the Galaxy =)=) (^^) (00)(00) Acknowledgements During this thesis there have been plenty of people who have made things easier for me or helped guiding my brain towards solutions, or simply just lifted my spirits by being the bee’s knees. First and foremost, I want to thank Michael Kramer for providing me with the opportunity to come working in Bonn. Without you, I wouldn’t have met all the fantastic people here. Even with your busy schedule, you still manage to squeeze in time for all the students, providing them with valuable input. To my day-to-day supervisor, Laura Spitler, thank you. Seemingly at the drop of a hat you manage to make time for your students, and are always ready to listen to and give feedback to questions or any other issues that might arise. Furthermore; thank you for, noticing all my: punctuation mistakes. For post-docs applying here, it seems there is a strict requirement of being friendly and helpful. Ewan Barr, you are a bottomless pit of wisdom and apparently know everything about everything computer-wise. Especially during the PAF days, you were like a secondary supervisor, and I’m grateful for your help. Plus, it is hilarious how you turn your Scottish accent up to 11 when you celebrate Bacchus. To the post-docs that have at some point had offices in the madhouse that is the ground floor, Gregory Desvignes, Ralph Eatough, Charlie Walker, and the Roberts Main and Wharton, thank you for your various help throughout the years. I also want to thank my TAC: Ben Stappers, Olaf Wucknitz, Norbert Langer, Laura, and Michael. Thank you for listening to me complaining about all the things that didn’t work, and trying to find solutions to my problems. For a long time it really did feel like all my projects were cursed, but at least you guys were there to listen to me. To the trio that made things so much easier, and to an extent kept me away from the never-ending rabbit hole that is German bureauocracy, thank you. Kira Kühn, Mariya Halvadzhieva, and Tuyet-Le Tran, you guys are the treasure of MPIfR. Of course one can not observe without a telescope. Alex Kraus, the wizard of Effelsberg scheduling, thank you for all your efforts. To the Effelsberg operators, thank you for all your help with observations. To the people who led me to the path that brought me to Bonn, Vilhelm Sigfús Sig- mundsson (Fúsi), Páll Jakobsson, Gunnlaugur Björnsson, and Einar H. Guðmundsson, this is all your fault and I thank you for it. Where would one be without friends and loved ones? Nataliya Porayko, you are so many things packed into such small space. Sweet, passionate (aggressive?), caring, smart (sometimes tupoj), funny little babuska. I love you. Hans Nguyen, my brother that my mother did not give birth to. I don’t want to make these acknowledgements too long, so I’ll just say that you are the poster boy of a perfect friend, and people understandably envy our bromance.
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