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The Transient Radio Sky Observed with the Parkes Radio Telescope

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The Transient Radio Sky Observed with the Parkes Radio Telescope The transient radio sky observed with the Parkes radio telescope Emily Brook Petroff Presented in fulfillment of the requirements of the degree of Doctor of Philosophy February, 2016 Faculty of Science, Engineering, and Technology Swinburne University i Toute la sagesse humaine sera dans ces deux mots: attendre et espérer. All of human wisdom is summed up in these two words: wait and hope. —The Count of Monte Cristo, Aléxandre Dumas ii Abstract This thesis focuses on the study of time-variable phenomena relating to pulsars and fast radio bursts (FRBs). Pulsars are rapidly rotating neutron stars that produce radio emission at their magnetic poles and are observed throughout the Galaxy. The source of FRBs remains a mystery – their high dispersion measures may imply an extragalactic and possibly cosmological origin; however, their progenitor sources and distances have yet to be verified. We first present the results of a 6-year study of 168 young pulsars to search for changes in the electron density along the line of sight through temporal variations in the pulsar dispersion measure. Only four pulsars exhibited detectable variations over the period of the study; it is argued that these variations are due to the movement of ionized material local to the pulsar. Our upper limits on DM variations in the other pulsars are consistent with the scattering predicted by current models of turbulence in the free electron density along these lines of sight through the interstellar medium (ISM). We also present new results of a search for single pulses from Fast Radio Bursts (FRBs), including a full analysis of the data from the High Time Resolution Universe (HTRU) sur- vey at intermediate and high Galactic latitudes. No new FRBs were found in the intermedi- ate latitude survey and five new bursts were found at high latitudes. The unexpected dearth at intermediate latitudes is found to be inconsistent (with 99% confidence) with an isotropic distribution using previously published rates. From the 9 FRBs at high latitude an all-sky rate can be derived with the largest sample of FRBs to date of R (F 0.6Jyms)> FRB ≥ +4.2 3 1 1 +3.2 3 5.7 2.7 10 (95%) FRBs sky− day− ,orRFRB(F 2Jyms)=2.5 1.6 10 (95%) − ⇥ ≥ − ⇥ 1 1 FRBs sky− day− . Although lower than previously published estimates, these rates are still inconsistent with results at intermediate latitudes. The FRBs from the HTRU survey were re-observed in a detailed follow-up campaign to place limits on possible repeating sources. No repetition was detected from any of the FRBs; however, a new burst was discovered in real-time during these observations: FRB 140514. Polarization information for the burst was preserved by the real-time search pipeline at Parkes, and the burst was found to be 21 7% circularly polarized. Multi- ± wavelength follow-up was also performed and no variability was detected in the field related to the burst. These observations placed the first limits on an afterglow. The full search of the HTRU intermediate and high latitude survey also resulted in the discovery of 50 “perytons”, seemingly dispersed terrestrial signals of unknown origin. We ⇠ present conclusive evidence that perytons are caused by on-site microwave ovens producing sparks in a non-linear shut down phase. Based on the properties of the perytons and FRBs iii we conclude that the observed FRBs cannot be produced by the microwave ovens on site and an astrophysical origin remains highly favored. iv v Acknowledgments It’s difficult to find the words to fully express my gratitude to all the people who deserve it. There were a lot of people who helped make this happen from when I decided I wanted a PhD when I was twelve. Early thanks are due to Bill Lamb, Rosa Hemphill, Catherine Garland, and all the people at Oregon Episcopal School who let me do my own thing as well as to Cindy Blaha and everyone in the Carleton College physics department. I owe my love of pulsars and my introduction to radio astronomy to the one and only Joel Weisberg. Thank you, Joel, for working patiently with me for over three years at Carleton and for introducing me to Australia and to Parkes. I would never be here writing this if it weren’t for you. Before going any further enormous and heartfelt thanks go to my amazing supervisors: Willem van Straten, Simon Johnston, and Matthew Bailes. Willem – thank you for pro- viding support, encouragement, counsel, and wisdom over the last three years. Your good judgment has helped me navigate the world of research and made me a better person. Simon – thank you for giving me one of the greatest gifts a supervisor ever could, the space and freedom to speak my mind. I’ve been learning from you since my first trip to the ATNF back in 2009 and it has been an honour. Matthew – thank you for showing me what quality research looks like and giving me something to aspire to. Wisdom doesn’t just come from supervisors. I’m grateful to the friends who I have had along the way who have taught me in one way or another. Jonathan, thank you for the book recommendations, the debates, the coding lessons, the chocolate, and saving me from my terrible cooking. Dave, thank you for your endless positivity, your encyclopedic movie knowledge, and for basically carrying our team at trivia (bonus points for your specific Star Trek theme song knowledge). Jonathan and Dave, thanks for making Scotch Saturday happen. Tyler, thank you for being a friend through thick and thin, laughing with me, and showing me how a good thesis is done. Rebecca, thank you for being you, for having an infectious amount of happiness about the world around you and for picking me up whenever I got down. Evan, thank you for your counsel and for being willing to listen when asked and give advice when greatly needed. Ewan, thank you for always encouraging me to do my best, push outside my comfort zone, not be afraid, and for reminding me that things will turn out OK. Enormous thanks to Andrew for answering my questions – from the embarrassingly simple to the ridiculously technical. And a great big thank you to the rest of the pulsar group for everything along the way: Paul, Stefan, Pablo, Fabian, Manisha, Shivani, Vivek, vi Vikram, Damien and Ian. I would also like to acknowledge all the mentors who have given me advice, support, direction, and encouragement in one way or another during these past three years (in no particular order): Katie Mack, Bryan Gaensler, Brian Schmidt, Elaine Sadler, Tamara Davis, Naomi McClure-Griffiths, Michael Childress, Fang Yuan, Chris Blake, Alan Duffy, Virginia Kilborn, Karl Glazebrook, Jeff Cooke, Michael Murphy, Sarah Maddison, Tyler Pritchard, George Hobbs, Antonia Rowlinson, Dick Manchester, Keith Bannister, Tara Murphy, Kate Gunn, Sue Lester, Elizabeth Thackray, John Sarkissian, John Reynolds, Phil Edwards, Brett Presig, Mal Smith, JP Macquart, Cath Trott, Ron Ekers, Ben Stap- pers, Andrea Possenti, Jasson Hessels, Aris Karastergiou, Sarah Burke-Spolaor, David Champion, and Michael Kramer. Swinburne, CSIRO, CAASTRO, and Parkes have been supportive and fantastic envi- ronments in which to work and I wish I could thank the entire community individually. You’ve all encouraged, motivated, inspired, and impressed me during my time here. Believe it or not I would also like to thank those out there who caused me pain, both mental and physical – the ones who said I’d never make it. Proving you wrong has been one of the most rewarding experiences of my life. Natasha, thank you for being my best friend for 10 years and reminding me every time I come back why Portland is home. Norma, thank you for being my biffle, my other Wonder Twin, and my robot unicorn. Special thanks to Hallie, Becca, Bizou, Tug, and Sanny, even though you’re not people and you’ll never read this. Pakey, thank you for listening; I aspire to be as good of a person as you. Erica, just thank you. Thank you for being my sister. I’d especially like to thank my mom and dad for supporting me from the very beginning, giving me all a daughter could want, and always being on the other side of the door, or the phone, or the Skype call when I wanted to quit and said I couldn’t do it, saying “Yes you can”. I love you both more than anything. vii viii Declaration The work presented in this thesis has been carried out in the Centre for Astrophysics & Supercomputing at Swinburne University of Technology (Hawthorn, VIC), the Australia Telescope National Facility/CSIRO Astronomy and Space Sciences (Marsfield, NSW) and the CSIRO Parkes radio telescope (Parkes, NSW) between 2012 and 2015. This thesis contains no material that has been accepted for the award of any other degree or diploma. To the best of my knowledge, this thesis contains no material previously published or written by another author, except where due reference is made in the text of the thesis. The content of the chapters listed below has appeared in refereed journals. Minor alterations have been made to the published papers in order to maintain argument continuity and consistency of spelling and style. Chapter 3 has been published in Monthly Notices of the Royal Astronomical Society, • 435, 1610, 2013, as “Dispersion measure variations in a sample of 168 pulsars”, au- thored by E. Petroff, M. J. Keith, S. Johnston, W. van Straten, and R. M. Shannon. Chapter 4 has been published in Astrophysical Journal Letters, 789,L26,2014,as • “An absence of fast radio bursts at intermediate galactic latitudes”, authored by E.
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