Recent Virgo/LIGO Results And Future Prospects Florent Robinet - PowerPoint PPT Presentation

LIGO-G0900655-v3 Recent Virgo/LIGO Results And Future Prospects Florent Robinet Journées SF2A, July 2009 Florent Robinet

Gravitational Waves Gravitational waves = "ripples" in space-time They obey a wave equation - propagation speed = c - two transverse polarizations ( + and x ) Dimensionless amplitude given by h Production of gravitational waves 2  R  2  c  6 R s 5 c v ℒ = G  A good GW source : - is compact and massive - is asymmetric - has a relativistic speed Lab production Astronomical sources 2 one-ton masses, 2 m apart, rotating at 1kHz h~10 -21 Looking at a distance of 1  (~300 km) : h~10 -39 Worth a try... Not even a chance ! Journées SF2A, July 2009 Florent Robinet

Sources of Gravitational Waves Supernovae Unexpected Compact Binary Systems (Black holes / Neutron stars ) ? Pulsars Cosmic strings Stochastic background Journées SF2A, July 2009 Florent Robinet

Detection of Gravitational Waves free mass h ~ L L L-  L Beam splitter L laser free mass − 18 m  L ~ 10 L+  L L photodiode GW Journées SF2A, July 2009 Florent Robinet

Detection of Gravitational Waves free mass h ~ L L L-  L Beam splitter L laser free mass − 18 m  L ~ 10 L+  L L photodiode GW Main Sensitivity factors : ● Arm length  high finesse Fabry-Perot cavity ● Laser power ● Mechanical and thermal stability of the free masses  suspensions, coating... Journées SF2A, July 2009 Florent Robinet

The Virgo Interferometer History 1989 : proposal 1992 : french approval 1996 : construction starts 2001 : tests on the central itf 2003 : commissioning starts 2007 : first science run (VSR1) Characteristics Located in Italy (Pisa) 3 km long arms Cavity finesse : 50 1 st Science Run : May  Oct 2007 : VSR1 Duty cycle = 81% Long locks (up to 94h) Range for a 1.4-1.4 M ⊙ system : ~4Mpc 2 nd Science Run 7 th of July 2009  … : VSR2 Journées SF2A, July 2009 Florent Robinet

The Virgo Sensitivity Sensitivity improvements Journées SF2A, July 2009 Florent Robinet

The Virgo Noise budget Noise budget Sum of modeled noise Measured sensitivity Journées SF2A, July 2009 Florent Robinet

Detectors Network Virgo (3 km) LSC – Virgo collaboration Full data sharing since May 2007 Livingston (4 km) Geo (600 m) Hanford (4&2 km) Journées SF2A, July 2009 Florent Robinet

Detectors Network Coincidence between detectors → Reduction of the false alarm rate → Background estimation S5 / VSR1 S6 / VSR2 Livingston Hanford 1 Livingston Hanford 1 Virgo Hanford 2 Virgo Journées SF2A, July 2009 Florent Robinet

Detectors Network SOURCE POINTING ● Source location within a few degrees ● Serious candidates follow-up (EM, neutrinos...) t Virgo SOURCE t Livingston GHOST t Hanford t Hanford Journées SF2A, July 2009 Florent Robinet

Searches for GW Signals Data = stream of noise Parameterized waveforms (template bank) are searched in the data : Matching template/data  Signal-to-noise ratio (SNR) Ideally : high SNR events = GW events BUT : real data have glitches  non-Gaussian noise whitened data Templates Search strategies : ● Use of clean data (data quality studies) ● Coincidence in time and parameters between detectors ● Target search in space and time (GRBs, pulsars...) ● Additional cuts (  2 , mass, amplitude...) ● Background estimation (time-offset between detectors or off-source time) ● Search efficiency computed thanks to hardware and software injections Journées SF2A, July 2009 Florent Robinet

Searches for GW Signals Compact Binary Coalescence Characteristics : ● BH-BH, NS-NS or BH-NS systems ● VSR1 range ~ 4 Mpc (NS-NS, 1.4-1.4 M ⊙ , SNR=8) ● Total mass < 500 M ⊙ ● Waveforms computed in the general relativity framework ● Free parameters : mass, spin and orbits ● Inspiral / Merger / Ringdown phases Merger 3 mass regions : Inspiral ● "Low mass" ( 2 < M < 35 M ⊙ ) : Post-Newtonian waveforms ● "High mass" ( 25 < M < 100 M ⊙ ) : IMR waveforms Ringdown ● "Black holes ringdown" ( M < 500 M ⊙ ) : Damped sinusoid Can provide information about : ● Strong field gravity ● Dense matter ● Population of massive bodies in the universe ● Cosmology (standard candles) ● Sources of GRB ● Astrophysics of the source Journées SF2A, July 2009 Florent Robinet

Searches for GW Signals Burst Signals , see also talk by M. Was Characteristics : ● Short lived signals (~1 ms ⇒ ~1 s) ● Broad-band search : ~50 Hz to a few kHz ● Unknown or poorly known waveforms ● Minimal or no assumption about the waveforms ● Search open to the unexpected ● Multiple analysis pipelines Sources ● Supernovae core collapse ● Merger / ringdown of binary compact objects ● Neutron stars instabilities ● Cosmic string cusps ● Unexpected signals... Dimmelmeier et al., astro-ph/0702305 Journées SF2A, July 2009 Florent Robinet

Searches for GW Signals Continuous Signals Pulsar Signals : ● Targeted search (~ 200 known pulsars w/ f spin > 20 Hz) 1 / 2 1 / 4 snr ~ t snr ~ t ● Integrated signal (targeted search : , all-sky : ) ● Assumption f GW = 2 f spin Can provide information about : ● Ellipticity ● Solid quark star ? ● Internal magnetic field ? ● Energy budget of the star spin-down Stochastic Background Signal : ● Early Universe GW Background ( ~ CMB) ● Integrated signal ● Constraints on  GW . S5 preliminary result :  GW < (1.0 ± 5.2)10 -6 (it surpasses the Big-Bang nucleosynthesis bound) Journées SF2A, July 2009 Florent Robinet

Recent Highlights Search for gravitational wave bursts in S5 LIGO runs Isotropic detection efficiency SG rates vs. strength exclusion curves Journées SF2A, July 2009 Florent Robinet

Recent Highlights Search for gravitational waves from low mass compact binary coalescence (S5) 1.4 x 10 -2 L 10 -1 yr -1 3.6 x 10 -3 L 10 -1 yr -1 7.3 x 10 -4 L 10 -1 yr -1 5.0 x 10 -4 L 10 -1 yr -1 6.0 x 10 -5 L 10 -1 yr -1 6.0 x 10 -5 L 10 -1 yr -1 5.0 x 10 -5 L 10 -1 yr -1 2.0 x 10 -6 L 10 -1 yr -1 4.0 x 10 -7 L 10 -1 yr -1 ● S5/VSR1 under internal review ● High mass under internal review ● BH ringdown : in progress Journées SF2A, July 2009 Florent Robinet

Recent Highlights Search for gravitational waves produced by pulsars (S5) ● Upper limit on the Crab pulsar : Energy loss by GW radiation < 2% ● Upper limit for J0537-6910 : h 0 < 4.4 10 -26  < 1.3 10 -4 ● Upper limit for J1952+3252 : h 0 < 2.9 10 -25  < 2.7 10 -4 Virgo should contribute significantly at low frequency (Vela pulsar) Journées SF2A, July 2009 Florent Robinet

Recent Highlights Search for gravitational waves produced by cosmic strings cusps (S4) Excluded @ 90% S5 / VSR1 analysis is on-going It should set competitive limits over the parameter space Journées SF2A, July 2009 Florent Robinet

Recent Papers 7 Papers were submitted/published in the last 3 months - Search for gravitational-wave bursts in the first year of the fifth LIGO science run - Stacked Search for Gravitational Waves from the 2006 SGR 1900+14 Storm - Search for High Frequency Gravitational Wave Bursts in the First Calendar Year of LIGO's Fifth Science Run - First LIGO search for gravitational wave bursts from cosmic (super)strings - Search for gravitational wave ringdowns from perturbed black holes in LIGO S4 data - Einstein@Home search for periodic gravitational waves in early S5 LIGO data - Search for Gravitational Waves from Low Mass Compact Binary Coalescence in 186 Days of LIGO's fifth Science Run + Papers on the joint LSC-Virgo search are to come Journées SF2A, July 2009 Florent Robinet

A Path to Detection 2003 2008-2009 Virgo starts Virgo+ and eLIGO commissioning upgrades C7 VSR1 VSR2 VSR2 S4 S5 S6 TODAY 2005 2009-2011 LIGO reaches nominal Joint Run sensitivity S6-VSR2 DETECTION Unlikely Could be... 1 st GENERATION Journées SF2A, July 2009 Florent Robinet

S6 / VSR2 Preparation Virgo upgrades (Virgo+) : ● Same infrastructure ● Increase the laser power (from 8 to 17 W today and to 25 W eventually) ● Thermal Compensation System (TCS) of the mirrors ● New input mode cleaner ● New control electronics ● New mirrors for a higher cavity finesse ( next year ) ● Monolithic suspension ( next year ) Gain in sensitivity TCS Journées SF2A, July 2009 Florent Robinet

S6 / VSR2 Preparation Commissioning efforts to reach design sensitivities VIRGO VIRGO Used to be ~ 4 Mpc (S5/VSR1) Journées SF2A, July 2009 Florent Robinet

S6 / VSR2 Preparation Online Analysis : Trigger spectrogram ● Bursts and CBC analysis pipelines are run online (latency < 1 h) ● Data of the 3 detectors are put in coincidence ● Source direction is extracted ● False alarm rate can be tuned ● Data quality is monitored ● Hardware injections are performed SNR > 5 SNR > 10 SNR > 20 ● Crucial factors : low latency, good pointing accuracy, low false alarm rate ● Low latency triggered searches (GRB, SN...) ● Follow-up of best candidates at other astronomical observatories Optical : Wide field, Radio, X-ray (Swift, TAROT...) Neutrinos detectors : (Super-K, Antares, IceCube...) ⇒ T. Pradier's talk TAROT Journées SF2A, July 2009 Florent Robinet