Towards a precision description of precessing black-hole-binaries

Lead Research Organisation: Cardiff University
Department Name: School of Physics and Astronomy


Accurate models of the gravitational-wave signal emitted by generic configurations of black-hole binaries as they inspiral and collide, are essential to make gravitational-wave detections and perform astrophysics with the Advanced LIGO and Virgo detectors, which are due to come online in late 2015. One of the most pressing problems is the modelling of generic binaries, where the black-hole spins introduce wild dynamics that generate complicated waveforms. We currently have a preliminary waveform model, but this does not take into account the subtle precession effects at the black holes approach merger, or their effect on the waveform as the final black hole rings down. It is also important, for both gravitational-wave searches and measurements of physical parameters, to determine
those physical parameters that have the dominant effects on the waveform structure, and are therefore the parameters that can be most precisely measured. This has an impact both on how we construct waveform models, and on the astrophysical questions that can be answered with gravitational-wave observations. Several research directions are possible, including modelling the late-inspiral
waveforms of generic systems, using these models to estimate the physics that can be measured from GW observations, and devising strategies to use these models to search for GWs and to measure source parameters.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/N504002/1 01/10/2015 31/03/2021
1797917 Studentship ST/N504002/1 01/10/2016 31/03/2020 Eleanor Hamilton
Description The main outcome of this award is the production of a model of the gravitational wave signal produced by two colliding black holes. Specifically, this model concerns systems where one or both of the black holes is spinning in a direction that is not perpendicular with the plane in which the black holes are orbiting each other. This kind of system is known as a 'precessing binary'. This is the first model in which the effects of the precession have been tuned to numerical relativity, allowing for a much more precise and accurate description of the system than has previously been achieved. The work funded through this award also contributed to the production of a catalogue of numerical waveforms for precessing binaries. This catalogue covers a much wider range of parameter space than existing catalogues of such waveforms and so allows us to extend our understanding of the effects of precession to more extreme systems. As part of the production of this model and as a result of studying the waveforms in our catalogue we have been able to observe and model previously unknown or unmodelled features of precessing systems.
Exploitation Route The model produced over the course of this award can be used in future detections and the analysis of gravitational waves by the LVK collaboration. It will be used to obtain more accurate estimates of the properties of the systems producing gravitational waves (such as the masses and spins of the black holes making up a binary). This will in turn allow for more accurate inferences about the populations of astrophysical objects in the universe (are most of the black holes above a certain mass? are they spinning or non-spinning?) which will help in drawing conclusions as to how they were formed. The model can also be used in tests of general relativity with gravitational waves, which require very precise models of general relativity predictions of gravitational wave signals, in order to compare them with the detected signals and look for deviations from general relativity.
Sectors Other

Description Outreach Event (Star Attractions, National Museum Cardiff) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A free interactive event aimed at all ages hosted at the National Museum Cardiff. The School of Physics and Astronomy manned a few tables featuring a range of physics and astronomy-based demos and volunteers discussed the concepts presented with members of the general public.
Year(s) Of Engagement Activity 2017,2018
Description Royal Society exhibit 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Members of the general public as well as school groups visited the Royal Society Summer Science Exhibition. I assisted on a stall presenting Gravitational Waves ("Listening to Einstein's Universe) and discussed the exhibits with visitors.
Year(s) Of Engagement Activity 2017
Description School visit 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact A group of ~20 sixth form pupils visited the School of Physics and Astronomy for a series of workshops and lectures throughout the day in order to provide an insight into research in the department.
Year(s) Of Engagement Activity 2018