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And the quest for gravitational waves A.Viceré – INFN Firenze/Urbino for the Virgo Collaboration.

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Presentation on theme: "And the quest for gravitational waves A.Viceré – INFN Firenze/Urbino for the Virgo Collaboration."— Presentation transcript:

1 and the quest for gravitational waves A.Viceré – INFN Firenze/Urbino for the Virgo Collaboration

2 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 2/63 Plan of the talk Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

3 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 3/63  Linearized Einstein eqs. (far from big masses) admit wave solutions (perturbations to the background geometry)  GW: transverse space-time distortions propagating at the speed of light, 2 independent polarization Ripples in the Cosmic Sea

4 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 4/63 Coupling constants  In SN collapse withstand 10 3 interactions before leaving the star, the gravitational waves instead leave the core undisturbed  Very early GW decoupling after Big Bang –GW  s (T  GeV) –  1 s (T  1 MeV) – γ  s (T  0.2 eV) stronge.m.weakgravity 0.11/ Ideal information carrier, Universe transparent to GW all the way back to the Big Bang!! GW emission: very energetic events but almost no interaction

5 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 5/63 PSR : GW do exist  Pulsar bound to a “dark companion”, 7 kpc from Earth.  Relativistic clock: v max /c   GR predicts such a system to loose energy via GW emission: orbital period decrease  Radiative prediction of general relativity verified at 0.2% level P (s) (9) dP/dt-2.425(10)· d  /dt (º/yr) (18) MpMp ± M  McMc ± M  Nobel Prize 1993: Hulse and Taylor

6 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 6/63  Luminosity:  Amplitude: Plausible target GW amplitude Compactness C 1 for BH 0.3 for NS for WD h ~ Example target amplitude: coalescing NS/NS in the Virgo cluster (r ~ 10 Mpc) Efficient sources of GW must be asymmetric, compact and fast GW detectors sensitivity expressed in amplitude h : 1/r attenuation

7 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 7/63 Synopsis of sources LONG DURATIONSHORT DURATION MATCHED FILTERING TEMPLATE-LESS METHODS Rotating NS Coalescing compact binaries Stochastic GWSupernovae

8 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 8/63 Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

9 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 9/63 Principle of Detection Need to measure:  L ~ m Target h ~ Cluster) Big challenge for experimentalists! Feasible L ~ 10 3 m GW induce space-time deformation Measure space-time strain using light Interference fringes Credit: M.Lorenzini

10 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 10/63 How much is m? Size of the UniverseVirgo clusterGalactic centerTarget GW wavelengthsNeutron star radiusWavelength of YAG laserSize of an atomProton radius Virgo sensitivity 1 Light-year log 10 r

11 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 11/63 A real detector scheme Laser 20 W Output Mode Cleaner 3 km long Fabry-Perot cavities: to lengthen the optical path to 100 km Input Mode Cleaner Power recycling mirror: to increase the light power to 1 kW Virgo optical scheme

12 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 12/63 Master laser, 1W Slave laser, 22W Main Beam Path F.I. E.O. F.I. Laser

13 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 13/63 Super mirrors Fused silica mirrors 35 cm diam, 10 cm thick, 21 kg Scattering losses:a few ppm Substrate losses: 1 ppm Coating losses: <5 ppm Surface deformation: /100

14 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 14/63 VIBRATION ISOLATION Thermal noise Superattenuator: filters off the seismic vibrations.

15 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 15/63 Requirements mbar for total pressure mbar for hydrocarbons Vacuum enclosure 7000 m 3

16 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 16/63 Plan of the talk Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

17 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 17/63 The GW detectors network LIGO – Livingston, LA VIRGO, Pisa, Italy GEO600, Hannover, D LIGO – Hanford, WA A network of 4 (5) GW detectors Virgo and the LIGO Scientific Collaboration have signed a MoA for full data exchange and joint data analysis and publication policy

18 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 18/63 Virgo: 3km arms LAPP – Annecy NIKHEF – Amsterdam GPG - Birmingham RMKI - Budapest INFN – Firenze-Urbino INFN – Frascati INFN – Genoa LMA – Lyon INFN – Napoli OCA - Nice LAL – Orsay APC – Paris INFN – Padova-Trento INFN – Perugia INFN – Pisa INFN – Roma 1 INFN – Roma 2 POLGRAV – Warsav

19 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 19/ h (Hz -1/2 )‏ Virgo LIGO Resonant antennas Hz GEO Core 10 Mpc BH-BH Merger 100 Mpc Pulsars h max – 1 yr integration BH-BH Inspiral, z = 0.4 BH-BH Inspiral, 100 Mpc QNM from BH Collisions, Msun, z=1 NS,  =10 -6, 10 kpc QNM from BH Collisions, Msun, 150 Mpc NS-NS Inspiral, 300 Mpc NS-NS Merger 100 Mpc 1 st generation detectors Design sensitivity curves Credit: P.Rapagnani

20 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 20/63 LIGO Scientific Collaboration Commissioning started in Design sensitivity achieved end 2005 Detector technology demonstrated ! LIGO S1 - Aug 23, 2002 – Sep 9, 2002 S2 - Feb 14, 2003 – Apr 14, 2003 S3 - Oct 31, 2003 – Jan 9, 2004 S4 - Feb 22, 2005 – March 23, 2005 S5 - November 2005 – Fall year of 3 det. coincident data

21 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 21/63 Virgo sensitivity evolution

22 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 22/63 FIRST SCIENCE RUN (VSR1)  From May 18 to Oct  Joined LIGO S5  The detector demonstrated excellent stability  Sensitivity improved during the run, exploiting short interruptions Duty cycle: 84% Longest lock: 94 hours Avg. Lock Duration: 11.2 hrs Lock Recovering Time: ~30 min BNS Inspiral Range (Mpc)

23 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 23/63 Recent progress  Reaching the design sensitivity and being limited by fundamental noises is all but simple  One has to fight with many little technical noises, often unpredicted and unmodelled  Most relevant: scattered light triggered by environmental noise, eddy currents, magnetic couplings, thermal transients

24 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 24/63 VIRGO vs LIGOs & GEO600  Same HF sensitivity  LIGO slightly better in the mid range  Virgo much better at LF  GEO600 not competitive A factor 2-3 still missing at low frequency. WHY? The big step forward in the last decade has been the demonstration of the interferometers technology. The design sensitivity has been (almost) reached and stability is so good (unexpectedly) that an efficient network could be created. Virgo, now, has opened the road to very low frequency region.

25 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 25/63 Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

26 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 26/ Science Runs So Far S1S2S3S4 S5 LIGO: GEO: VSR1 Virgo: 368 days of triple-coincident LIGO data  Since end of S5 / VSR1 : – ► Upgrading LIGO 4-km interferometers and Virgo – ► GEO and LIGO 2-km interferometer taking data whenever possible for “AstroWatch” vigil

27 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 27/63 Unmodeled burst searches  Supernova collapse: dynamics and waveform badly predictable –Estimated rate: several /yr in the VIRGO cluster, but the efficiency of GW emission is strongly model dependent –Simulations suggest E GW ~10 -6 M ʘ c 2, but NS kick velocities suggest possible strong asymmetries GW emitted secs hrs [Zwerger, Muller]

28 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 28/63 All-Sky Burst Searches  The most-recent published results use S4 data  LIGO-only search [ Classical and Quantum Gravity 24, 5343 (2007) ] – ► Searched days of triple-coincidence data (H1+H2+L1) for short (<1 sec) signals with frequency content in range Hz – ► No event candidates observed – ► Upper limit on rate of detectable events: 0.15 per day (at 90% C.L.) – ► Sensitive to GW energy emission as small as ~10  7 M  at 10 kpc, or ~0.25 M  at the distance of the Virgo Cluster  LIGO-GEO joint search [ CQG 25, (2008) ] –First use of fully-coherent network analysis for burst signals  S5 / VSR1 all-sky search is currently under internal review –Factor of ~2 better amplitude sensitivity, and much longer observation time –Doing coherent network analysis using LIGO and Virgo data

29 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 29/63 Gravitational Waves from Soft Gamma Repeaters  SGRs are believed to be magnetars –Occasional flares of soft gamma rays –May be associated with cracking of the crust that excites vibrational f-modes of the neutron star  LIGO searched for GW signals associated with SGR flares –Dec “giant” flare of SGR 1806–20 –190 flares from SGR 1806–20 and SGR during first year of S5 –Placed upper limits on GW signal energy for each flare –[ PRL 101, (2008) ] –Within the energy range predicted by some models  LIGO also searched for GW signals matching the quasiperiodic oscillations seen in X-rays in the tail of the Dec giant flare –Placed upper limits [ PRD 76, (2007) ]

30 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 30/63 Coalescing binaries  Pairs of compact stars, like PSR , but close to the final “coalescence” –PBH: Primordial Black Holes (in the galactic halo): M in [0.2, 0.9] –BNS: Binary neutron stars: M in [0.9, 3.0] –BBH: Binary black holes: M in [3, 20]  Inspiral signal accurately predictable –Newtonian dynamics –Post-Newtonian corrections (3PN, (v/c) 11/2 ) [L.Blanchet et al., 1996]  Recent big progress in merger 3D simulation [Baker et al 2006, Praetorious 2006] –Crucial to extract physics, mostly encoded in the merger phase chirp [Campanelli et al., PRL, 2006]

31 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 31/63 Binary Inspiral Searches 100 Mpc [ Preprint arXiv: ]  New result from first year of S5 data  No inspiral signals detected  Using population models, calculated 90% confidence limits on coalescence rates:  For binary neutron stars: 3.8×10 –2 per year per L 10  For 5+5 M  binary black holes: 2.8×10 –3  For BH-NS systems: 1.9×10 –2  (Slightly tighter limits if BHs are assumed to have no spin)

32 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 32/63 GRB  Short, hard gamma-ray burst –Leading model for short GRBs: binary merger involving a neutron star  Position (IPN) consistent with being in M31  LIGO Hanford detectors were operating –Searched for inspiral & burst signals  Result from LIGO data analysis: No plausible GW signal found; therefore very unlikely to be from a binary merger in M31  [ ApJ 681, 1419 (2008) ]  Hundreds of GRB occurred during the live time of LIGO and Virgo detectors: still under analysis

33 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 33/63 Spinning Neutron Stars  Non-axisymmetric rotating NS emit periodic GW at f=2f spin but…weak  SNR can be increased by integrating the signal for long time (months) ‏  10 9 NS in the galaxy, 163 known in LIGO/Virgo band  Doppler correction of Earth motion needed (  f/f  ): blind search limited by computing power Data from ATNF Pulsar Catalogue (www.atnf.csiro.au/research/pulsar/psrcat)

34 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 34/63 Searches for Periodic Signals from Known Radio/X-ray Pulsars  Demodulate data, correcting for motion of detector –Doppler frequency shift, amplitude modulation from antenna pattern –For a triaxial star, expect GW signal at twice the spin frequency  S5 preliminary results (using first 13 months of data): –Place limits on strain h 0 and equatorial ellipticity  Crab ►  limits as low as ~10 –7 It’s plausible that an ordinary neutron star could sustain an ellipticity as large as ~10 –6 ; Some models allow larger

35 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 35/63 Searches for a Stochastic Background of Gravitational Waves  Weak, random gravitational waves should be bathing the Earth –Left over from the early universe, analogous to CMBR ; or due to overlapping signals from many astrophysical objects / events  Results from LIGO S5 data analysis –Searched for isotropic stochastic signal with power-law spectrum –For flat spectrum, set upper limit on energy density in gravitational waves: –Preliminary result from ~half of S5 data:  0 < 1.3 × 10 – 5 –Starts to constrain cosmic (super)string and “ pre-Big-Bang ” models –Final S5 result to be released soon, with factor of ~2 better sensitivity – will dip below Big Bang Nucleosynthesis bound  Or look for anisotropic signal: [ PRD 76, (2007) ] (S4 data)

36 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 36/ Log( f [Hz])‏ Log (  0 h )‏ Laser Interferometer Space Antenna - LISA Inflation Slow-roll Cosmic strings Pre-big bang model EW or SUSY Phase transition Cyclic model CMB Pulsar Nucleosynthesis Advanced IFOs, 1 yr data Expected   h < 7x LIGO S1, 2 wk data   h < 23 PRD (2004) LIGO S3, 2 wk data   h < 8 x PRL (2005)‏ A broader look at the stochastic background Credit: B.Sathyaprakash Initial LIGO, 1 yr data Expected   h < 2x10 -6

37 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 37/63 Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

38 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 38/63 1st generation detection chances 1 ST GENERATION INTERFEROMETERS CAN DETECT A NS-NS COALESCENCE AS FAR AS VIRGO CLUSTER (15 MPc) LOW EXPECTED EVENT RATE: ev/yr (NS-NS) FIRST DETECTION: POSSIBLE BUT UNLIKELY

39 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 39/63 First step to improve: Virgo+  Important technology progress achieved in the last years. It is possible to upgrade Virgo now, enhancing the sensitivity by 2-3 (and the rate by one order of magnitude)  The Virgo+ package: –more laser power (20  50 W) – compensation of mirror thermal lensing –better electronics –change of input mode cleaner mirror –monolithic suspensions  LIGO also undergoing similar upgrades, towards Enhanced LIGO

40 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 40/63 2 nd generation detectors  Virgo and LIGO have achieved the design sensitivity. Data still under analysis, but the expected event rate is low ( ev/yr)  To increase the chance of first detection and to open the way to GW astronomy we want to enhance the amplitude sensitivity by x10 (hence the detection rate by x1000!)  Advanced LIGO (USA): funded by NSF. In construction  Advanced Virgo: Conceptual Design e Preliminary Project Execution Plan submitted to funding agencies (INFN and CNRS). Facing a project review process to get approved ly Enhanced LIGO/Virgo Virgo/LIGO Credit: R.Powell, B.Berger Adv. Virgo/Adv. LIGO 2014

41 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 41/63 Advanced LIGO Projected Sensitivity  Advanced LIGO is approved and funded; construction has begun  Expect to be operational starting in 2014 or 2015 Factor of ~10 in amplitude sensitivity Factor of ~1000 in volume Hz 10 –24 10 –23 10 –21 –22

42 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 42/63 Adv design features tilt control fused silica suspension fibers heavier mirrors low dissipation coating larger spot high finesse cavity high power laser (200 W) signal recycling DC detection moreover…  better vacuum  environmental noise reduction  low noise electronics  … compensation of thermal lensing

43 Binary NS sight distance in AdV AdV: ~150 Mpc Advanced LIGO: ~170 Mpc each detector

44 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 44/63 Virgo upgrade plans Virgo+ installation Advanced Virgo Virgo+ Virgo Science Run 2 Virgo+ commissioning Installation of monolithic suspensions (?) Virgo Science Run 3 Advanced Virgo installation Advanced Virgo commissioning Advanced Virgo Science Run yr Mpc BNS inpiral range – expected progress

45 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 45/63 Triangulation allowing to pinpoint the source A network allows to deconvolve detector response and regress signal waveform --> measure signal parameters, including source distance for BNS signals Benefits by the LIGO-Virgo network False alarm rejection thanks to coincidence Joint operation yields a longer observation time, and a better sky coverage LIGO VIRGO

46 BNS events: will we ever see them? Empirical models  Use observed (4) galactic binary systems coalescing on timescales comparable to Universe age  Infer # of events/Milky Way Equivalent Galaxy  Assume galactic density 0.01 Mpc -3 Population synthesis models  Use galactic luminosity to deduce star formation rate  Alternatively, use supernova events to calibrate the number of massive stars  Model binary formation and evolution to deduce # of systems coalescing in less than Hubble time

47 BNS: AdV predictions Empirical model rather uncertain  Small number of systems observed, little statistic Population synthesis still unconclusive  Strong dependence on models  AdV alone sees from O(1) to O(10) events/year AdV to operate together with Advanced LIGO!  Combined sight distance may exceed 300 Mpc  Network will see from O(10) to O(100) events/year

48 BBH sight distance AdV: ~ 700 Mpc

49 BBH: pop. synth. predictions Notes  Sight distance is effective: takes into account the distribution of masses in the population synthesis  Only masses < 10 M are simulated BBH population synthesis very uncertain  Merger rates vary by factors of hundreds  If model A is true, prospects of detection are dim!  However...

50 BBH: empirical prediction IC10 X-1  Binary system in local group (~ 700 kpc)‏  Includes a BH, m~24 M o, and a massive Wolf-Rayet star, m~ 35 M o Allows to predict a rate (Bulik et al.)‏  The WR will evolve in BH, without disrupting the binary system  The resulting system should have M chirp ~14M o  Such systems are detectable by AdV up to 1.1 Gpc...  Rate for AdV should be ~ 250 /year Rate for combined Advanced LIGO – AdV ~ 2500/year

51 Known pulsars: AdV limits on h Dots: spin down limits. Beaten by AdV for about 40 known objects

52 Stochastic background limits with AdV H1 - L1H1 - V1 One year of operation of AdV – AdLIGO  Will improve over nucleosynthesis bounds by several orders  For comparison, LIGO S5 results should be just below BBN limit  AdV contribution depends on the exponent n of the stochastic background model, and is more relevant for larger n

53 Astrophysical backgrounds A network can locate point sources of random GW signals  Such could be objects of astrophysical interests, for instance very large black holes in active galaxies  LIGO – Virgo network, with multiple baselines, improves sensitivity by 25% at equator and by 42% at poles, over LIGO only  Source localization is improved by a factor O(10)‏

54 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 54/63 Advanced Detectors will see GWs  The technology of interferometric detectors has been demonstrated  A further step in sensitivity appears necessary to open the way to physics and astronomy. Some sources appear certain, unless astrophysical assumptions are wrong  To make science, a multimessenger approach will be mandatory

55 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 55/63 Few words about gravitational waves Working principles of GW detectors The large interferometers in the world, and Virgo A personal choice of science results LSC-Virgo joint observation perspectives Towards GW astronomy: multimessenger opportunities

56 Targeting SNe; low energy 's... Boost detection confidence  Neutrino and GW expected within a few ms delay  Very tight coincidence can be required Constrain mass strongly  1ms accuracy: m < 1eV constrain

57 High energy 's KM3Net and IceCube will see with E up to 100's GeV  Coverage of Southern and Northern sky  Reconstruction capabilities in the 1° range  Common targets: GRB's, SGR giant flares, etc...

58 Targeting GRB events Swift now, Fermi (GLAST) keep looking at  rays from GRB GRB powered by accretion disks on newly formed objects Neutrino and GW expected within a few ms delay Short GRB (< 2s) potentially related to BNS, BH-NS Long GRB (>2s, average 30s) related to (classes of) SNe  Again, boost detection confidence  Provide insight in the fireball mechanism

59 Other messengers... Radiotelescopes  Crucial, f.i. to “lock” on pulsar signals (Automated) Optical telescopes  To alert GW detectors of interesting events  To follow up triple coincidences observed in GW detectors X-ray telescopes  Privileged eyes on the hot material falling into compact objects  For instance, in LMXB  Another eye at GRB events ..

60 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 60/63 Beyond the 2° generation? Where and how can we reduce the detector noise? Seismic Thermal Shot High power laser Better optics New optical configuration QND techniques New materials Cryogenic interferometers Underground detectors

61 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 61/63 ET, THE “ULTIMATE” DETECTOR  Underground facility to minimize seismic noise  Mirrors held at cryogenic temperature  Longer arms, new geometry E.T. - Einstein gravitational-wave Telescope  Design Study Proposal funded by EU within FP7  Large part of the European GW community involved (EGO, INFN, MPI, CNRS, NIKHEF, Univ. Birmingham, Cardiff, Glasgow) Credit: H.Lück

62 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 62/63 0.1m 10m 1 Hz k 4x10 7 4x10 5 4x10 3 M  frequency f / binary black hole mass whose freq at merger=f Current detectors 3 rd generation Adv detectors LISA h (1/ √ Hz) ‏ Credit: B.Sathyaprakash

63 Bologna – February 19th, 2009 A.Viceré – Università di Urbino & INFN Firenze 63/63 I recall lessons at a summer school in theoretical physics in Parma in 1997: detectors still mostly on paper. General skepticism This seminar in 2009: 1° generation detectors demonstrated! LIGO and Virgo upgrading towards 2° generation We hope that 2° generation will allow to start GW ASTRONOMY! To make the most science of it, close cooperation with the astrophysical community will be a must. Conclusions?


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