Gravitational-wave astronomy with LIGO and Virgo

Marc van der Sluys

March 11, 2010

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Abstract: The LIGO-Virgo collaboration has at its disposal three independent kilometre-scale gravitational-wave (GW) interferometers: the two LIGO detectors in the USA and Virgo in the EU. After upgrades and commissioning in the last two years, these interferometers are now in their enhanced stage, and roughly twice as sensitive as the initial detectors. While much effort is undertaken to search for GW signals in the data, our work focuses on the detailed follow-up analysis of candidate compact binary coalescence (CBC) events found in such searches. I will discuss our work on the extraction of astrophysically relevant data from (so far simulated) GW events. Once a CBC signal has been found, we can use the information from the search trigger to do detailed parameter estimation. The binaries that LIGO and Virgo are sensitive to consist of stellar-mass black holes and/or neutron stars. We use a Bayesian framework and developed a Markov-chain Monte-Carlo (MCMC) code which computes the probability-density function (PDF) for all physical binary parameters, including masses, distance and sky position. Our code is the first to take into account the spins of the binary members. From the PDF, we can not only obtain the ‘best value’ for each parameter, but also the accuracy of that value. I will present our MCMC code and the typical accuracies with which the parameters can be determined from GW observations. I will show that while spins make our work more complicated, our results would be biased if they were not taken into account.