update on s5 search for grb and gravitational wave burst coincidence isabel leonor university of...
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Update on S5 Search for GRB and Gravitational Wave Burst Coincidence
Isabel Leonor
University of Oregon
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 2
Outline of GRB-GWB search search for short-duration gravitational-wave bursts (GWBs) coincident with
gamma-ray bursts (GRBs)
use GRB triggers observed by satellite experiments Swift, HETE-2, INTEGRAL, IPN, Konus-Wind include both “short” and “long” GRBs
search 180 seconds of LIGO data surrounding each GRB trigger
(on-source segment)
waveforms of GWB signals associated with GRBs are not known
use crosscorrelation of two interferometers (IFOs) to search for associated GW signal
use crosscorrelation lengths of 25 ms and 100 ms to target short-duration GW bursts of durations ~1 ms to ~100 ms
use bandwidth of 40 Hz to 2000 Hz
i ii
j kj k
crosscorrx y
x y2 2
correlated signal in two IFOs large crosscorr
180 seconds
sample GRB lightcurve
(Swift)
LIGOIFO 1
LIGOIFO 2
triggertime
crosscorrelateoutput of two IFOs
look for largestcrosscorrelation
within 180-secondon-source segment
use 180-secondLIGO on-sourcedata surrounding
GRB trigger co
unts
/sec
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 4
Estimating probability of measured on-source largest crosscorr: Sample off-source distribution using 25-ms cc length
apply search to off-source segments to obtain crosscorrelation distribution
use time shifts to get enough statistics
largest crosscorrelation found in on-source search indicated by black arrow
probability is estimated using this distribution
off-source crosscorrelation distribution is determined for each IFO pair for each GRB trigger
plocal = 0.57
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 5
The GRB Sample for the S5 Run, as of March 3, 2007
153 GRBs as of March 3, 2007 ~70% with double-IFO
coincidence ~40% with triple-IFO
coincidence ~25% with redshift ~10% short-duration GRBs
z ~ 0.3 z ~ 1.3
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 6
GRB positions
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 7
Preliminary search results, 25-ms crosscorrelation
no data quality cuts used search GRBs up to
GRB 070227 use V2 calibrations when
available (i.e. up to April 2006), otherwise use V1 calibrations
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 8
Do excess events come from a particular time epoch? test: remove events from
September and October 2006 removing some other pair of consecutive months doesn’t result in same reduction in significance further study needed
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 9
Preliminary search results, 100-ms crosscorrelation
search GRBs up to GRB 070227
will application of data quality cuts improve results?
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 10
hrss sensitivity, sine-gaussian, 250 Hz, linear polarization
mean hrss50 = 7.6E-22 Hz-1/2
peak hrss50 = 6.3E-22 Hz-1/2
mean hrss90 = 3.7E-21 Hz-1/2
peak hrss90 = 2.8E-21 Hz-1/2
50% confidence
90% confidence
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 11
hrss sensitivity, sine-gaussian, 250 Hz, circular polarization
mean hrss50 = 7.2E-22 Hz-1/2 E = 0.2 Msun at 20 Mpc (merger model)
peak hrss50 = 5.6E-22 Hz-1/2
mean hrss90 = 8.9E-22 Hz-1/2 E = 0.3 Msun at 20 Mpc (merger model)
peak hrss90 = 7.1E-22 Hz-1/2
50% confidence
90% confidence
Due to modifications to the code, all GRBs, even those at bad positions, have determinable LHO-LLO upper limits (so far).
March 17, 2007 Baton Rouge, LA
Burst F2F Meeting I. Leonor 12
hrss upper limit vs. average antenna factor (LHO)