Title: The LIGO Scientific Collaboration is currently analysing LIGO data from the Third Science Run S3 for
1Status 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.