oct 2006 g.modestino1 Experimental results correlating GW detector data and Gamma Ray Bursts Giuseppina Modestino LNF ROG Collaboration INFN – LN Frascati, LN Gran Sasso, Sez. Roma 1, Roma 2 and Genova Universities “La Sapienza” and “Tor Vergata” Rome, L’Aquila, Geneve CNR –IFN Roma INAF –IFSI Roma CERN - Geneve

oct 2006 g.modestino2 Summary Search for GW Burst Signals and resonant cryogenic detectors. GW and GRB association EXPERIMENTAL IMPLICATIONS. Data analysis under two hypotheses COSMIC RAYS DETECTION analogies and calibration Experimental results Previous and in progress

oct 2006 g.modestino3 GW Burst Sources Binary system coalescence Supernovae ms pulsars Search for GW Burst Signal SNR ~ 10 3 (10kpc/d) 2 ( Hz -1 /h 2 ) (  f /1Hz) d = distance from earth h = detector spectral density  f = bandwidth of detection

oct 2006 g.modestino4 Cryogenic resonant detectors GW detection sensitivity ALLEGRO AURIGA EXPLORER NAUTILUS Search for GW Burst Signal SNR ≥ 10 for a galactic event h = ÷ Hz -1/2  f = 1 ÷ 50 Hz

oct 2006 g.modestino5 Initial operation of the International Gravitational Event Collaboration G.A. Prodi et al. (IGEC Collaboration) Int. Jour. of Modern Physics D 9, 237 (2000) Study of coincidences between resonant gravitational wave detectors P. Astone et al. (ROG Collaboration) Class. Quantum Grav. 18, 243–251 (2001) First search for gravitational wave bursts with a network of detectors Z.A. Allen et al. (IGEC Collaboration) Phys. Rev. Lett. 85, (2001) Search for gravitational wave bursts by the network of resonant detectors P. Astone et al. (IGEC Collaboration) Class. Quantum Grav. 19, 1367–1375 (2002) Study of the coincidences between the gravitational wave detectors EXPLORER and NAUTILUS in 2001 P. Astone et al. (ROG Collaboration) Class. Quantum Grav. 19, 5449–5463 (2002) Methods and results of the IGEC search for burst gravitational waves in the years 1997–2000 P. Astone et al. (IGEC Collaboration) Phys. Rev. D 68, Search for GW Burst Signal

oct 2006 g.modestino6 Typical theoretical prediction for GW burst amplitude:  l/l = h = kHz 1Mpc (M GW /10 -2 M o ) 1/2 (10 -3 s/  GW ) 1/2 f(kHz) R(Mpc) [10 55 erg/s] Gravitational wave luminosity 24 6 Time [ms] Ruffert et al.,AA 311,532 (1996) associated to a single GRB 1 kHz  GW = 1ms (M GW ) 1/2 R( Gpc ) h ~h ~

oct 2006 g.modestino7 GW Burst Detection Strategy List of candidate events obtained selecting (with an adaptive threshold) data produced by filter matched to a delta Search for coincidences Data Analysis Experimental Tools Statistical excess L ocal mass distribution for the directional studies + time reference Statistical association Link with GRBs (GRB=systematic phenomenon)

oct 2006 g.modestino8 ASSOCIATION WITH SUPERNOVAE Measurements with the resonant Gravitational Wave detector EXPLORER during the GRB No anomaly in the background of the GW data detector with the sensitivity of h>= (ROG Coll.) Astron. Astrophys. Suppl. Ser Search for GW associated with the GRB using the LIGO detector. None candidate event detected in the signal time region of 180s [ -120s, + 60s ] around t  (LIGO Coll.) Phys.Rev. D 72, (2005)

oct 2006 g.modestino9 Statistical association Search for Time Correlation Between GRBs nd Data from the Gravitational Wave Antenna EXPLORER. Coincidence technique. No evidence in a time window of + 1 s, at several delays. (ROG Coll.) Astron. Astrophys. Suppl. Ser. 138, 603 –604 (1999) Correlation between GRBs AND GWs. Using 120 GRBs, in a 10s time window, an U.L. of was obtained. (AURIGA Group) Phys.Rev. D 63, (2001) Search for Correlation between GRBs detected y BeppoSax and gravitational wave detectors EXPLORER AND NAUTILUS Cross-correlation technique- Absence of signal of amplitude h> within s. (ROG Coll. )Phys. Rev. D 66, (2002 ) h> s. Cumulative analysis of the association between the data of the GW detectors NAUTILUS and EXPLORER and GRBs detected by BATSE and BeppoSAX. Analysis of the data relative to a large number of GRBs detected during the ‘90s, allows to exclude GW burst signal with h> (ROG Coll. )Phys. Rev. D 71, (2005) Experimental studies:

oct 2006 g.modestino10 Zero-threshold search: better sensitivity than the "event" method for the expected "small" signals. 1)Combine the GW detector data E(t) with the same relative time with respect to the N GRB arrival time t 0 E1E1 E2E2 E3E3 EnEn  t(s) t  t GRB 2)Applying a cumulative algorithm:  =  i N -1/2 For the single data stretches  i =

oct 2006 g.modestino11 EXPLORER is equipped with 3 layers of Plastic Scintillators 2 above the cryostat - area 13m 2 1 below -area 6 m 2 ) NAUTILUS is equipped with 7 layers of Streamer tubes 3 above the cryostat - area 36m 2 /each 4 below -area 16.5 m 2 /each) Cosmic Ray detectors Studing the effects of the showers on the crygenic bars

oct 2006 g.modestino12 Unfiltered signal (V 2 ) The signal after filtering (kelvin) The effect of the Cosmic Ray Shower on NAUTILUS A true mechanical pulse The cosmic ray effect on the bar is measured by an offline correlation, driven by the arrival time of the cosmic rays, between the observed multiplicity in the CR detector and the data of the antenna, processed by a filter matched to  signals

oct 2006 g.modestino13 The effects of th CR on resonant GW detectors Thermo-acoustic model

oct 2006 g.modestino14 kelvin Time [s]  E ~ kelvin Zero-threshold search Cosmic-ray showers interacting with NAUTILUS Astone et al. (ROG Coll.) PRD, 84, 14, Astone et al. (ROG Coll.) Phy. Lett. B (2001) Astone et al. (ROG Coll.) Phys. Lett. B (2002) 2001 In agreement with the thermo- acoustic model = K  ~ K 2000

oct 2006 g.modestino15 Time delay between the two emissions The typical amplitude of a GW burst, on Earth, associated to a single GRB, is: It implies an intrinsic difficulty relating the upper limit on the amplitude, in general, interpreting the measurement results M 1/2 R(Gpc) But there is no clear predictions about  t=|t GRB -t GW | h = R = distance M = amount of GW energy emitted (Mo) By experiment, it is possible to solve the problem, correlating the data of 2 GW detectors Essentially, two methodologies are possible: Coincidence analysis Cross-correlation technique (advised in nonstationary noise conditions)

oct 2006 g.modestino16 Searching for GW signals under variable delay hypothesis The basic idea of the analysis is the simultaneity of the signal on two GW detectors. Apply the usual data selection criteria evaluating the temperature noise in the time interval around the GRB time Select and cross-correlate data of the coincident intervals of the two GW detectors. Apply the usual cumulative algorithm to the cross- correlation function Phys. Rev. D (2002) Phys. Rev. D (2002)

oct 2006 g.modestino17 n EXPLORER(CERN) n ON from March to December n T = 2.6 K n Duty Cycle = 91% n Average sensitivity h= NAUTILUS (LNF ) n ON from January to December n T = 1.5 K n Duty Cycle = 80% n Average sensitivity h= Search for GW signal in a 800 s interval time Beppo-Sax Catalog 2001

oct 2006 g.modestino18. Cross-correlation analysis. The data with T eff < 20 mk are selected. 47 GRB are analyzed T eff evaluated within a time window of + 400s, centered at t GRB EXPLORER NAUTILUS

oct 2006 g.modestino19 (ROG Coll), Phys. Rev. D (2002). Cross-correlation result EXPLORER x NAUTILUS 2001 R( t ’ ) cross-correlation function (averaged on the 47 GRBs) relative to the energy of the two GW detectors. -400s <  t ’ < +400s h < % t ’(s)

oct 2006 g.modestino20 Searching for simultaneous GW signal GRB list = BATSE + Beppo-Sax GW detectors = EXPLORER +NAUTILUS GWB arrival time = GRB Peak Time ± 5 s GW data background over 30 minute periods with temperature noise t n < kelvin (Peak Time ± 15 min) Cumulative average and median algorithm ROG Coll. PRD 71, (2005) Zero-threshold search

oct 2006 g.modestino21 GRBs Database ROG Coll. PRD 71, (2005) Searching for simultaneous GW signal.

oct 2006 g.modestino22 ROG Coll. PRD 71, (2005) Data selection Effective temperature Te distribution computed in 1150 time intervals around each GRB peak time N=387 data stretches with Te < 15 mK are selected

oct 2006 g.modestino23 E(0) = 6.33 mk Searching for simultaneous GW signal. = 6.30 mK  = 0.13 mK ROG Coll. PRD 71, (2005) GW detector energy as a function of the GW-GRB delay Combine min GW data stretches For each time delay, the median value Em is extracted h <

oct 2006 g.modestino24 sin 4  correspondingly to the 387 selected GRB arrival times and theoretical isotropic distribution The 4 regions of increasing sin 4  separated by vertical lines, correspond to the data subsets separately analyzed. Searching for a correlation with sin 4   ROG Coll. PRD 71, (2005)  ~ sin 2 

oct 2006 g.modestino25 4/4 ROG Coll. PRD 71, (2005) Looking for a correlation with sin 4  SNR of the excess at zero delay of the median value

oct 2006 g.modestino26 GW resonant detectors EXPLORER + NAUTILUS And SWIFT  events An example : t =  trigger time+0.5s Year 2005  events with z < 1 Interval time for background evaluation :100s In progress: Data Analysis

oct 2006 g.modestino27 Data Taking during 2005

oct 2006 g.modestino28 EXPLORER and NAUTILUS NAUTILUS EXPLORER Hz -1/2  ~ Hz -1/2 EXPLORER  ~ Hz -1/2  ~ Hz -1/2

oct 2006 g.modestino29 Output of the cumulative algorithm applied to EX+NA j=1,23 N=23  SWIFT events (11 EX+12 NA) K S  trigger time  Ej(t) / N Red -Sampling time 3.2 ms Black - Integrating on  0.5 s In progress:

oct 2006 g.modestino30 GW resonant detectors EXPLORER + NAUTILUS And Cosmic Rays Analyze a similar (statistically) sample: t = CR trigger time+0.5s Year CR events ( with multiplicity>2000 part/m2) Interval time for background evaluation :100s Testing with Cosmic Rays Detection Apply the same procedure: In progress:

oct 2006 g.modestino31 Output of the cumulative analysis applied to EX+NA j=1,26 N=26  EAS events (13 EX+13 NA) K S EAS trigger time Red -Sampling time 3.2 ms Black - Integrating on  0.5 s  Ej(t) / N

oct 2006 g.modestino32 Search for GW Burst Signal Sensitivity of bar detectors

oct 2006 g.modestino33 Sensitivity of the bar detectors IGEC2

oct 2006 g.modestino34 Search for GW Burst Signal Upper limit for GW burst detection Class. Quantum Grav. 23 S57-S62 (2006)

oct 2006 g.modestino35 NAUTILUS EXPLORER bar length L = 3m mass = 2300 Kg material Al5056 resonance ~1 KHz temperature = 0.1 K - 2 K ROG - The two cryogenic detectors - LNF-Frascati CERN