Modelling compact objects for precision astrophysics

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We are entering an era of high-precision astronomy, both electromagnetic and gravitational. The first generation of highly sensitive gravitational-wave detectors have reached design sensitivity and are being upgraded using advanced technology. LOFAR is on-line, providing significant improvements in radio timing precision. Future advances associated with the SKA in radio, the Einstein Telescope and the space based detector LISA for gravitational waves will complement current quality X-ray observations, and will allow us to improve our understanding of the Universe significantly. To benefit maximally from these advances, we need to improve our current models of a range of phenomena involving compact objects. Better quality theory is needed both to detect the various signals and to probe as much of the relevant physics as possible.This research proposal builds on the Southampton General Relativity Group's expertise in black hole, neutron star and gravitational wave astrophysics, and is aimed at developing a deeper understanding of the dynamics of compact objects, the associated observational signatures and how signals can be used to probe the underlying physics. The programme is of a highly interconnected nature with three different themes requiring similar methodology (e.g., general relativistic perturbation theory or numerical simulations) and physics input (e.g., superfluidity, magnetic fields or gravitational radiation reaction). The overall aim is to develop significantly improved models that can be tested against future high-precision observations in a range of channels.Neutron stars are unique astrophysical laboratories, the modelling of which requires much poorly known physics. In order to investigate their properties, one must combine supranuclear physics with magnetohydrodynamics, a description of superfluids and superconductors, potentially exotic phases of matter like a deconfined quark-gluon plasma and, of course, general relativity. Achieving a better understanding of neutron star dynamics is one of the key aims of this proposal. We will carry out two parallel projects, focused on neutron star dynamics and relevant astrophysical scenarios. The proposed work is of immediate relevance for gravitational-wave physics, leading to astrophysically motivated signal searches, and provides useful insights into problems relevant for electromagnetic observations. We aim to construct accurate models of neutron star pulsations that can be tested against recent observations of oscillations associated with magnetar giant flares, and which will inform future targeted gravitational-wave searches for r-mode oscillations in fast spinning neutron stars. We will provide improved models of the enigmatic glitches and other timing phenomena seen in radio pulsars. We also plan to account for environmental effects, e.g., the role of the magnetosphere in the context of intermittent pulsars and effects due to variable torques in accreting systems relevant for X-ray timing observations.Inspiralling binaries are intrinsically the strongest sources of gravitational waves in the Universe. In particular, there are exciting prospects for LISA to detect the radiative inspiral of compact objects into massive black holes in galactic centres. Gravitational waveforms from such events are extremely efficient probes of the strong gravity near the massive black hole, and promise to allow accurate tests of gravitational theory in its most extreme domain. In order to realise this promise we need a good theoretical understanding of relativistic radiation-reaction effects. Recent progress on the problem of the gravitational self-force provides significant momentum for work in this area. Building on this, we will explore the promising synergy between self-force calculations, numerical relativity and post-Newtonian theory, in order to inform a universal model of binary inspirals across the entire range of mass ratios.