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The LIGO Scientific Collaboration is currently analysing LIGO data from the Third Science Run S3 for

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Title: The LIGO Scientific Collaboration is currently analysing LIGO data from the Third Science Run S3 for


1
Status of the Search for Spinning Binary Black
Holes in S3 LIGO data
Gareth Jones (Cardiff University, UK) on behalf
of the LIGO Scientific Collaboration
  • The LIGO Scientific Collaboration is currently
    analysing LIGO data from the Third Science Run
    (S3) for signals emitted by spinning binary
    black holes. Matched filter searches for these
    sources are complicated by the requirement to
    accurately capture the modulations of the emitted
    gravitational waveform caused by spin-induced
    precession of the orbital plane. In order to
    address this problem we use a phenomenological
    family of templates designed by Buonanno, Chen
    and Vallisneri. In this poster we present
    results from a search sensitive to asymmetric
    binaries with total mass in the range 11 to 27
    solar masses through S3 playground data. The
    efficiency of the search is measured using
    software injections of a physical family of
    waveforms.

Injections
The BCVSpin Detection Template Family
We perform injections of simulated waveforms in
order to test the efficiency of the filter
pipeline. To test the BCVSpin filters we are
performing injections of waveforms predicted by
post-Newtonian approximation. In total
approximately 3159 injections have been made into
H1 data and 2817 into L1 data. The magnitude and
orientations of the spins of the injected
waveforms were set randomly over the full range
of possible values.
Buonanno, Chen Vallisneri, Phys. rev. D 67,
104025 (2003), gr-qc 0211087
The BCVSpin templates describe generic
gravitational waves emitted by a spinning binary
black hole (SBBH) using 11 phenomenological
parameters.
  • The plot on the right shows the SNR of signals
    detected in coincidence between H1 and L1.
  • The strong correlation between the SNRs
    measured in the two detectors corroborates that
    the coincidences measured were due to the
    injected signals rather than spurious noise.

The templates are defined in the frequency domain
by the formula
  • The templates are valid for the
    adiabatic-inspiral regime
  • We use the parameter ffinal to terminate the
    template before non-linear effects occur
  • BCVSpin templates are used primarily for
    detection rather than parameter estimation
  • We can make empirical connections between the
    phenomenological and the physical parameters
  • The injected waveforms were randomly generated
    so as to be uniformly distributed in
    log(distance) in the range 50kpc to 50Mpc.
  • We have a detection efficiency gt 50 up until an
    effective distance of 4Mpc.
  • ? values relate to the component masses of the
    binary
  • ß to relates to its spin
  • as encode the amplitude and constant phase of
    the waveform
  • tc is the time of coalescence.

This plot shows a typical waveform emitted by a
SBBH. We can see clearly the modelling of the
modulation to the waves amplitude and phase
caused by the spin-induced precession of the
systems orbital plane.
  • The injected waveforms were generated so as to
    have uniform total mass in the range Mtotal
    (7-31)Msolar
  • We find that we detect injections with good
    efficiency between around 11 and 27 Msolar.

S3 Playground Analysis
In order to tune the search parameters, the
BCVSpin filters were used to analyse a subset
(approximately 10) of the S3 LIGO data called
the playground. The lower cut-off frequency used
in the search is 70Hz. Template banks with
minimal match of 0.95 were generated for the 3
LIGO detectors.
Coincident triggers
Before claiming a detection of a SBBH we would
demand that a waveform is detected in 2 or more
detectors within a predefined time window and
that both waveforms have similar ?0 and ?3 values
(indicating a similarity in the masses associated
with the waveforms)
  • This plot shows the number of templates
    generated for each detector plotted against GPS
    time for the duration of S3.
  • It was decided that we would concentrate the
    analysis on H1 and L1 data in order to reduce the
    computational cost of the search. This choice was
    also based on quality of the H2 data.
  • This plot shows a cumulative histogram of the
    absolute difference in time between triggers in
    H1 and L1 that have been found to be coincident
    with an injected waveform.
  • Using these plots we estimate the size of our
    coincidence windows. Having set the window sizes
    we time slide one set of detector data against
    the other before searching for coincident
    triggers.
  • These time slides allow us to estimate the
    background trigger rate.

The Venn diagrams below show the length of time
analysed by each detector and combination of
detectors for the SBBH search. On the left we
see the data that was initially analysed, on the
right the times analysed once H2 is neglected.
Since H1 is noisier when H2 is out of lock, we
only analyse data when both H1 and H2 are in
lock.

Future Developments
Full S3 (hrs) Playground (hrs)
A new metric and method for template placement is
currently in development which should allow us to
search for any given combinations of component
masses. We aim to use these new codes as part of
our future analysis of S4 data and beyond.
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