New frontiers in transient astrophysics: gravitational-wave multi-messenger events and exotic stellar explosions

How and where did the elements of the Universe form? How do stars live and die? What happens when two of the densest objects in the Universe crash into each other? Where do the brightest flashes of light in the Universe come from? What is the ultimate fate of the Universe? These are some of the questions that lie at the heart of the research to be undertaken by this fellowship. The fellowship will exploit the UK's premier sky survey to detect new transient objects in the Universe, and undertake innovative approaches to studying these objects in order to further our understanding of the Universe.

When massive stars, more than 8 times the mass of our Sun, reach the end of their lives, they collapse due to their own gravity and produce a neutron star or black-hole. During this rapid and catastrophic collapse, large amounts of chemically-enriched material is expelled into the Universe in an extremely luminous event known as a supernova. These chemically-enriched innards are essential for life as we know it, containing carbon, oxygen and iron. Through supernova explosions, these elements form the next generation of stars and planets, seeding the building blocks of life. Our understanding of supernovae is hampered due to time lags between telescopes discovering the supernova, and larger telescopes then taking detailed observations. This fellowship will create a world-leading rapid observatory network to overcome this. Using the UK-led GOTO telescope system to discover new supernovae and automatically triggering larger telescopes nearby, we will routinely perform detailed observations within hours of discovery, and minutes in some cases. Opening this new timescale of investigation provides vital diagnostics on the nature of the exploding stars (such as their size and mass) and the energetics and chemical makeup of the explosion itself. These are essential for us to build a complete picture of how different stars die, and how the chemical fingerprint of our Universe was formed.

After massive stars die, their journey is not quite complete - recent breakthroughs mean we can now detect them 'beyond the grave' as their neutron star and black hole corpses violently merge. A truly landmark moment in history occurred in 2015 when the LIGO/Virgo detectors found a completely new signal from the Universe: minute ripples in space-time. These ripples were caused by two black holes merging 1.3 billion light years away and are known as gravitational-waves - their detection was the fruition of a century-old prediction by Einstein. As well as seeing, with the detection of gravitational-waves, we are now 'hearing' the Universe.
Just as our senses combine to give us far more information than they do alone, so too does combining light we see and gravitational-waves we hear from astrophysical transients. This 'multi-messenger' era of gravitational-wave research began in 2017 with the first ever event discovered in both light (photons) and gravitational-waves. The event, named GW170817, was the result of two neutron stars colliding around 130 million light years away and became one of the most intensely studied objects in the Universe. The findings from this single event are mesmerising, but it also raised many further questions. We only have one example of this kind of event. To make progress we must observe a population of similar events to understand their diversity and how often they occur in the Universe. Finding these objects is not trivial however, and, akin to the 'needle in the haystack' problem, it requires rapidly looking at huge swathes of the night sky to find the single correct counterpart to the gravitational-wave signal. By developing the GOTO system, designed explicitly to perform this task, and leading analysis of new gravitational-wave multi-messenger events with premier international facilities, this project will be at the forefront of the international effort to realise the potential of this exciting new window on the Universe.

Understanding how our Universe works, our place in it and how we came to be, is possibly the most deeply engrained facet of human curiosity. Astrophysics, therefore, captures the public's attention in a quite unique way amongst fundamental research, and is an absolutely crucial gateway to inspire interest in STEM subjects across all ages and demographics. At the heart of maintaining this gateway is demonstrable leadership and breakthrough science from within the UK on some of the Universe's biggest questions, and the dissemination of this leadership and science to the wider public. The impact of my work will be dissemination of new frontier knowledge about the Universe to the wider public and inspiring the pursuit of STEM in education.
This fellowship will produce world-leading research on the exciting new field of gravitational-wave multi-messenger astrophysics, and maintain the UK's leading role in the emergence of this new way to study the Universe. It is not an overstatement to say the emergence of this field, beginning in 2017 with the first ever detection, has been a generational breakthrough in science. The discovery reignited a passion in scientific research, breaking through generally impassable barriers for other sciences and gained blanket coverage from every major news outlet, interviews with fundamental researchers on national television, and made terms like 'gravitational-waves', 'neutron star' and 'kilonova' part of the public lexicon. The fellowship will continue this momentum from within the UK on this new field, and produce research that will reach far beyond other areas of fundamental research to inspire difficult-to-reach sectors of society with the fascination of STEM, and change their perception of research and the scientific method. I have a clear plan laid out that will ensure the research of this fellowship reaches the maximal audience possible using novel techniques, with a particular focus on creating engaging outreach activities to school children.
Inspiring scientific interest and literacy in the public via these means is essential for informed decision-making and ensuring long-term stability, both economically and societally. Those further pursuing a STEM education as a result of this impact will develop essential skills in data analysis, critical thinking and problem-solving. Such skills are in great demand across many sectors from politics, commerce, finance and research and development. A rich source of world-leading scientific minds over the coming generations in the UK is also vital to tackle big challenges ahead, such as climate change and energy crises.
A core part of this impact rests on closing the connection between researchers and their results and other interested parties (external academics in other fields, journalists, or the wider public). This fellowship will rely heavily on, and produce, open data, and proprietary periods will be kept at a minimum where they may be required. Research outputs will be available in open access formats, and data and analysis methods will be similarly hosts by publicly-accessible repositories.
More widely, UKRI are heavily invested in the future of time-domain astrophysics - and therefore the focus of this fellowship. This is via commitments to facilities such as the Large Synoptic Survey Telescope, LIGO, the Laser Interferometer Space Antenna and the Extremely Large Telescope. Each project has demanded advances in engineering, material physics, computing infrastructure and big data management. World-leading engineering and data expertise has developed in the UK as a result of the science-driven development. My team and I will exploit the maximum science return from these facilities, maintaining the world-leading stance of the UK at the frontier of fundamental research. Such a stance is essential for the UK to be in strong position to shape the future direction of technical and industrial advances required for the next generation of facilities.