Investigations in Gravitational Radiation

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

Abstract

Einstein's General Theory of Relativity (GR) predicts that dynamical systems in strong gravitational fields will release vast amounts of energy in the form of gravitational radiation. Gravitational waves are ripples in the fabric of spacetime and travel from their sources at the speed of light, carrying information about physical processes responsible for their emission, obtainable in no other way. They are among the most elusive signals from the deepest reaches in the Universe. Experiments aimed at detecting them have been in development for several decades, but only now are sensitivities reaching levels where real detection is possible within a few years. The worldwide network of interferometric detectors includes the German-UK GEO600, the French-Italian Virgo and the American Laser Interferometer Gravitational-Wave Observatory (LIGO). These detectors have all reached sensitivities close to their design goals and have taken the most sensitive data to date. Cooperation amongst different projects enables continuous data acquisition, with sensitivity to a wide range of sources and phenomena, over most of the sky. Data from GEO, LIGO and Virgo, has already begun to impact our understanding of astronomical phenomena. For example, the most recent observations with these detectors have (a) shown that less than 2% of the Crab pulsar's radiated power is in gravitational waves, (b) ruled out merging binary neutron stars as the progenitor of GRB 070201 (if it occurred in M31) and (c) set a new best upper limit on the strength of the stochastic gravitational-wave background. While the present phase of observations (circa 2010-2011) have a real chance of producing the first detections - possibly from compact binary coalescences, there can be no guarantees. However there is great confidence that the advanced detectors will routinely observe gravitational waves. The Cardiff and Glasgow groups have initiated and led searches for astronomical sources, thanks to the algorithmic and analysis effort that has been supported since the first data taking runs began eight years ago. We propose a programme of continued improvement to GEO600 and to be involved in the characterization and analysis of the resulting data from GEO and the worldwide network of interferometers. In particular we will be carrying out searches for * coalescing binary neutron stars, neutron star-black hole binaries, and black hole binaries * bursts of gravitational waves that may originate from supernovae, and * continuous signals from pulsars and other rotating neutron stars. In parallel, we are proposing research and development on the detector front. Detector sensitivity is mainly limited by thermal noise associated with the substrates of the mirrors, their reflective coatings, and their suspension elements, as well as by noise resulting from the quantum nature of the light used to provide illumination. Thus our research is targeted towards making innovative improvements in these areas. In particular we are taking leading roles in the upgrading of GEO and LIGO in the areas of silica suspensions, optics and interferometry, and for enhancements to the Advanced LIGO program and future interferometers in the areas of dielectric and waveguide mirror coatings, silicon substrates and cryogenic suspensions. In summary, the goal of the Glasgow, Cardiff and Strathclyde groups is to lead the first direct detection of gravitational waves using detectors based on their innovative developments. Once this milestone is achieved, routine observations will help us use this radiation as an observational and theoretical tool to understand * cores of supernovae and neutron stars, * gamma-ray burst engines, * the interactions of black holes and neutron stars, etc. In particular, coalescing compact binaries are self-calibrating standard candles, or sirens, which will be a new precision tool for cosmology and will enable strong field tests of general relativity
 
Description Modelling gravitational wave sources and developing algorithms to detect them and estimate their parameters.
Exploitation Route Collaboration members will use the pipeline in the analysis of data from LIGO and Virgo.
Sectors Education

 
Description Royal Society University Research Fellowship
Amount £803,198 (GBP)
Funding ID 516002.K5869/R OG 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2007 
End 09/2014
 
Description STFC Advanced Fellowship
Amount £548,111 (GBP)
Funding ID ST/H008438/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 09/2010 
End 09/2015
 
Description GEO600 
Organisation University of Glasgow
Department Physics and Astronomy Department
Country United Kingdom 
Sector Academic/University 
PI Contribution Detector characterisation and data analysis; strategic plans, scientific motivation for improving detector sensitivity.
Collaborator Contribution Building the detector, maintaining the detector, detector characterisation and data analysis.
Impact A working gravitational wave detector, development of advanced technology for advanced and third generation detectors.
 
Description LIGO Scientific Collaboration 
Organisation LIGO
Country United States 
Sector Academic/University 
PI Contribution Search algorithms and software, data analysis and astrophysical interpretation, scientific motivation for improvement in detector sensitivity
Collaborator Contribution Building and maintaining the LIGO detectors
Impact Publications, conference plenaries, conference contributions
 
Description Black Hole Hunter 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This is an on-line game that is on display at every major/minor outreach activity undertaken by members of the 1000-strong LIGO Scientific Collaboration.

It has been translated to German, French and Spain and attracts of 1000's of unique hits every year.
Year(s) Of Engagement Activity 2008
 
Description Can you hear black holes 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact AThis was a Royal Society Summer exhibition. An estimated 4000 people passed through our stand in 3 days.

Exhibits were developed and in particular the online black hole hunger game was developed for the exhibition.
Year(s) Of Engagement Activity 2008