Short time domain coherent radio astronomy

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This proposal builds on recent breakthroughs in Very Long Baseline Interferometry (VLBI) to study the changing radio universe on very short timescales. Research at short time scales, from a few nanoseconds to seconds, is important because many of the most pressing questions in astronomy concern difficult-to-study, fleeting phenomena. Our group recently innovated new algorithmic approaches to VLBI that now allow us to study signals in these very short time windows. The development of these new tools broadly impacts compact object astrophysics, gravitational wave physics, and cosmology. Potential pulsar and Fast Radio Burst (FRB) precision distances from plasma lensing open the window to the accurate localization of nanohertz gravitational wave sources, while FRB propagation probes the cosmic baryon content. This research is likely to connect and substantially impact previously weakly linked fields. We recently used our new technique to characterize an extreme plasma lensing effect around the Black Widow pulsar. Though this pulsar has been studied for 30 years, our group was the first to develop a framework to interpret its fleeting changes in brightness because no researcher previously had the tools to analyze this ephemeral phenomenon that lasts only a few milliseconds. The importance of this finding is that the plasma lensing effect functions as a magnifying glass that allows us to study deep space phenomena with previously unthinkable precision. We have demonstrated how we can use this effect to map the emission regions of a pulsar located 6,500 light years away with kilometre-level resolution. This unprecedented feat is equivalent to measuring the width of a hair on Mars from Earth. Improving our understanding of plasma lenses and their use to study short time domain phenomena will be the major focus of this program. Short-term objectives include: 1. Understanding Interstellar Lenses: Plasma lensing effects have the potential to revolutionize radio astronomy but their nature and geometry are unknown. We will use VLBI scintillometry to map plasma lenses in the interstellar medium. 2. Using Plasma Lenses as Telescopes: We will also use VLBI scintillometry to better explore the use of scattering screens as interstellar plasma lenses. 3. Using Lensing Effects to Study FRBs: The nature of FRBs is one of the most perplexing enigmas in astrophysics and a major front for research. We will use our technique to attain a systematic spatial localization of FRBs.