Theory Meets Data Analysis at Comparable and Extreme Mass Ratios - 2010

In this talk I will show recent results obtained by the RIT group fromsimulations of highly-spinning binaries including new data that givesnear maximal spins and high-mass ratio binaries. Simulations in bothof these regimes are numerically challenging. However asastrophysical binaries are expected to be highly-spinning and havehigh mass ratios accurate simulations in these regimes are crucialfor understanding the dynamics of realistic binaries.

We present simulations of non-spinning unequal mass black-hole binaries with mass ratio q=1/4 covering approximately 11 orbits prior to coalescence and merger obtained with the moving puncture technique. Accuracy of the simulations and matching to post-Newtonian waveforms is discussed.

In this talk we present the motivation behind our implementation of and results from a coherent search for spinning compact binary coalescences. Our method uses the Physical template family of waveforms which describe binaries where only one of the objects has spin. In addition we discuss the possibility of extending thissearch to incorporate template waveforms for precessing black hole mergers derived from numerical relativity.

A coherent multi-site search is expected to be more powerful than itscoincident counterpart in discriminating gravitational wave (GW) signals fromthe noise background. This is because the former tests the consistency of thesignals' amplitudes phases and time-delays across the sites with those expected from a real GW source. However the coherent statistic that is optimalin Gaussian noise is not guaranteed to perform as well in real data which arenon-Gaussian. Here we introduce an alternative coherent statistic for searchingcompact binary coalescence (CBC) signals that includes chi-square andnull-stream discriminators for non-Gaussian features in the data. Thisstatistic has been found to perform better than coincident statistics exploredin real data. This alternative coherent statistic is being used in ongoinginspiral-merger-ringdown searches in LIGO-Virgo data and is expected to beuseful in bridging the performance gap between the coincident CBC searchpipeline and the coherent burst search pipeline for detecting signalshigh-mass CBCs especially for systems with total-mass tending toward ahundred solar masses that have only a few signal cycles in band. We planto use this statistics in future NINJA analysis.

The familiar post-Newtonian inspiral description of a binary neutron star system is sufficient for detection in current instruments. However, as we consider making astrophysical measurements using advanced detectors, the effects of matter and strong gravity on gravitational wave signals may become significant. I will review recent work modelling the waveforms produced by the inspiral and coalescence of binary neutron stars. In the mid-to-late inspiral this includes modifications to the post-Newtonian waveform models from tidal deformations. In the late inspiral and coalescence, numerical simulations are exploring a range of masses, mass ratios, equations of state, and magnetic fields. In some circumstances a hypermassive remnant produces significant additional signal after the merger. Numerical simulation results also link neutron-star merger to potential counterpart signals.

Black hole-neutron star binary (BHNS) mergers are likely sources for detectable gravitational radiation and candidate engines for short-hard gamma-ray bursts. However, accurate modeling of these mergers requires fully general relativistic simulations, incorporating both relativistic hydrodynamics for the matter and Einstein's field equations for the (strong) gravitational fields. I will review techniques and results from recent fully general relativistic BHNS merger simulations. These simulations examine the effects of the BH:NS mass ratio, BH spin, and NS equation of state, focusing on both the gravitational waveforms and remnant disk.