Investigations in Gravitational Radiation - Support of LIGO Observing Run 3

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This application relates to STFC ST/N005430/1.Einstein's General Theory of Relativity predicts that dynamical systems in strong gravity fields will emit vast amounts of energy in the form of gravitational waves. These waves are ripples in the very fabric of spacetime, that spread out from their sources at the speed of light, and carry information about physical processes that created them. While powerful, the distortion of spacetime created by the waves is incredibly small, making them challenging to detect. For several decades STFC has been a partner in the LIGO project, which operates kilometer-scale detectors with cutting edge technology. On 14 Sept 2015, Einstein's theory was confirmed spectacularly when LIGO detected gravitational waves from the violent merger of a pair of black holes in a distant galaxy. Since then gravitational waves from a further nine black-hole mergers have been confirmed. In addition, on 17 August 2017 LIGO and its partner observatory Virgo detected gravitational waves from the merger of a pair of neutron stars -- burned out cores of dead stars. Comparison of gravitational signal to light emitted in the collision lead to several spectacular breakthroughs in astrophysics and cosmology. These included a direct measurement of the expansion rate of the Universe (the "Hubble constant"), and strong evidence that most of the heavy elements in the Universe such as gold and platinum are produced in these neutron star mergers.The worldwide network of detectors includes the American advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), the French-Italian-Dutch-Polish advanced Virgo, and the German-UK GEO600, plus the KAGRA detector under construction in Japan. LIGO and Virgo will start the third observing run in early-mid 2019, pooling their data in the hunt for further black holes, neutron stars, and other exotic phenomena. The research supported by this grant will help to extend the scientific benefit from the new data. Dedicated researchers will develop techniques for determining the location of merging black holes and neutron stars in the moments around or even before the final collision, enabling astronomers to study the light given off in the critical first minutes following the merger. They will also investigate how we can infer the as-yet-unknown interior structure of neutron stars from the gravitational-wave signal, thereby probing the properties of matter under some of the most extreme conditions found in the Universe.