Andersson STFC - General Relativistic Astrophysics

The last year has seen a string of outstanding successes in gravity and relativistic astrophysics. The breakthrough detection of gravitational waves from merging black holes provided a clear demonstration of the discovery potential of this new area of astronomy. As the sensitivity of gravitational-wave instruments improves, and a wider network of detectors come online, a broader range of sources is expected to be detected. Observations of the late stages of binary neutron star inspiral and merger are anticipated with particular excitement, especially since such events may have counterpart electromagnetic emission (e.g. short gamma-ray bursts). As we enter the era of gravitational-wave astronomy in earnest, there are many reasons for enthusiasm. The LISA Pathfinder demonstration of technology readiness of the drag-free interferometry required for space-based instruments, followed by the ESA selection of the LISA project (due for launch in the 2030s), ensures that gravitational physics will continue to develop for (at least) the next two decades. The main emphasis of gravitational-wave astronomy is on problems involving neutron stars and black holes. These fascinating and enigmatic objects involve truly inspirational science and represent unique laboratories for the exploration of the extremes of physics. Black-hole astrophysics impacts on a range of fundamental issues, from the nature of gravity to problems in cosmology, e.g., associated with structure formation in the early Universe. Meanwhile, neutron star observations allow us to probe the state of matter under extreme conditions, providing us with information which complements that gleaned from colliders like the LHC at CERN. The modelling of these highly relativistic systems involves a broad range of physics that is not accessible in the laboratory. As our observational capabilities improve, we are reaching the point where precise modelling is required both to interpret data and to facilitate the observations in the first place. The proposed research represents a coherent programme aimed at exploring the astrophysics of black holes and neutron stars in order to improve our understanding of the fundamental laws of physics of the Universe and reveal how nature operates on scales where our current understanding breaks down, a theme that remains central to the STFC mission. Neutron star modelling involves much complex physics and relates to a range of astrophysical phenomena, primarily probed by radio timing and X-ray timing and spectra. Neutron stars may also radiate detectable gravitational waves (through a variety of scenarios ranging from the supernova core-collapse in which they are born to the merger of binary systems). The challenge is to decode observed signals to constrain current theories, including the elusive equation of state for supranuclear matter. This proposal aims to improve our understanding of neutron stars, including their evolution and dynamics and how they interact with their environment. Black holes interact with their environment in a complex fashion. The modelling of this interaction provides a serious challenge. In particular, we need a precise description of the gravitational radiation-reaction-driven inspiral and eventual coalescence of binary systems. This problem is central for ongoing and future gravitational-wave searches. The gravitational capture of compact objects by massive black holes in galactic nuclei is particularly relevant for space-borne instruments like LISA, as the signal encodes information that allows high-precision tests of general relativity and precision studies of massive black-hole physics. A central objective for the proposed research is to model the inspiral dynamics in binary sources detectable by current ground-based and future space-based observatories.