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"DRAGNET: A high-speed, wide-angle camera for catching extreme astrophysical events"

Final Report Summary - DRAGNET (DRAGNET: A high-speed, wide-angle camera for catching extreme astrophysical events)

In the DRAGNET ERC Starting Grant project, we aimed to acquire insight into some of the most extreme and exotic phenomena in the Universe. Using the world's largest radio telescopes, supported by other premier telescopes operating at optical, X-ray and gamma-ray wavelengths, we searched for signals from neutron stars and other sources whose gravity and energy density push the limits of our theoretical understanding of physics.

In the last decade, astronomers have started detecting an enigmatic type of radio flash from the sky: a so-called `fast radio burst' or `FRB'. We now know that these FRBs originate from deep in extragalactic space, but we still don't know what produces them. During the DRAGNET project, we discovered that some FRBs can produce multiple radio bursts, and this means that their source must survive the energetic processes that produce the bursts. Using a variety of telescopes and techniques, we were able to localize this first-known repeating FRB to its host galaxy and discovered that it inhabits a star-forming region and is surround by a dense and extreme local environment. These observations have given a great boost to our theoretical modeling of this mysterious phenomenon but many questions remain, including whether all FRBs can repeat or whether these signals have multiple types of physical origins.

The DRAGNET project also made several important steps in our understanding of pulsars, which are highly magnetised, rapidly spinning neutron stars - the remnant cores of massive stars that have collapsed in a supernova. For example, we discovered a population of pulsars that transition into a state in which matter from a companion star influences their emission, and we studied pulsars that suddenly switch their behavior - apparently without any external influence. This has deepened our understanding of the fastest-spinning stars and the most extreme magnetic fields found in the Universe. We have also used pulsars as natural laboratories for probing the laws of physics: using a unique pulsar in a triple star system, we were able to show that Einstein's theory of gravity makes correct predictions for the orbital motions of these stars to within a few parts in a million.