LIGO Observational Results

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1 LIGO Observational Results Patrick Brady University of Wisconsin Milwaukee on behalf of LIGO Scientific Collaboration

2 LIGO Science Goals Direct verification of two dramatic predictions of Einstein s general relativity: gravitational waves & black holes Physics & Astronomy Detailed tests of properties of gravitational waves including speed, polarization, graviton mass,... Probe strong field gravity near black holes & in early universe Probe the neutron star equation of state Performing routine astronomical observations LIGO provides a new window on the Universe 2

hole mergers,... Coincident EM observations Surprises!

3 Astrophysical Sources of Gravitational Waves Bursts Supernovae: Neutron star birth, tumbling and/or convection Cosmic strings, black hole mergers,... Coincident EM observations Surprises! Stochastic background Big bang & early universe Background of gravitational wave bursts 3

least two interferometers & detailed examination of

4 Search Method: Time frequency decompositions Noise event: triggers and spectrogram Requires coincidence between at least two interferometers & detailed examination of instrumental & environmental behavior Simulated injection in hardware 4

5 Detection Efficiency Evaluate efficiency by adding simulated GW S4 bursts to the data. Example waveform Central Frequency Detection Efficiency S5 sensitivity: minimum detectable in band energy in GW EGW > 1 75 Mpc EGW > Mpc (Virgo cluster) 5

6 Upper Limits No GW bursts detected through S4 set limit on rate vs signal strength. CL Lower amplitude limits from lower detector noise S2 % 90 Rate Limit (events/day) d de clu Ex Lower rate limits from longer observation times S1 S4 projected S5 projected 6

Triggered Searches Follow up astronomical triggers, particularly gamma ray bursts Compare results with time shift background estimate No loud signals

7 Triggered Searches Follow up astronomical triggers, particularly gamma ray bursts Compare results with time shift background estimate No loud signals seen Look for cumulative effect Use binomial test to compare to uniform distribution No significant difference from expectation 54 GRB tests S2/S3/S4 result 7

8 Astrophysical Sources of Gravitational Waves Bursts Neutron star birth, tumbling and/or convection Cosmic strings, black hole mergers,... Coincident EM observations Surprises! Stochastic background Big bang & early universe Background of gravitational wave bursts 8

9 Signals from the Early Universe Cosmological GWs in the LIGO band (100 Hz) today were produced 10 22s after the big bang. Their detection would be very interesting! cosmic gravitational wave cosmic microwave background (10 22s) background (10+12s) 9

10 Procedure Search: cross correlate data streams x1, x2. Optimal statistic Y for all sky search is: Overlap Reduction Function Y= g(f)wgw (f) df x (f) x 2 (f) 3 N f P1(f)P2 (f) * 1 - detector noise spectra (determined by network geometry) γ(f) frequency (Hz) Test ΩGW(f) = Ωα(f/100Hz)α. II, August 2006 Most sensitivity from Hz TEV band (LHO LLO). 10

11 Predictions and Limits LIGO S1: Ω0 < 44 0 PRD (2004) H0 = 72 km/s/mpc 2 Log (Ω0) 4 Cosmic strings 6 PRL (2005) BB Nucleo Pulsar synthesis Timing Initial LIGO, 1 yr data Expected Sensitivity 8 10 LIGO S3: Ω0 < 8.4x10 4 CMB model 12 Inflation 14 Slow roll ~ 4x10 6 Pre big bang Advanced LIGO, 1 yr data EW or SUSY Expected Sensitivity Phase transition ~ 1x10 9 Cyclic model Log (f [Hz])

12 Astrophysical sources of gravitational waves Compact binaries Black holes & neutron stars Inspiral and merger Probe internal structure, populations, & spacetime geometry Spinning neutron stars Isolated neutron stars with mountains or wobbles Low mass x ray binaries Probe internal structure and populations 12

13 Gravitational waves from compact binaries LIGO is sensitive to gravitational waves from binary systems with neutron stars & black holes Waveforms depend on masses and spins. 13

14 Target Sources BBH: S2 S5 Ringdown: S4 S5 Component Mass, M 10 NS/BH spin important S3 S5 BNS S1 S5 1 PBH S2 S5 0.1 Binary Black Hole Coincidence with burst search Binary Neutron Star 1 3 Component Mass, M 10 Theory estimates upper bound of 1/year for LIGO during S5 Theory estimates upper bound of 1/3 year for LIGO during S5 14

15 Binary Neutron Stars S2 Observational Result cumulative number of events Phys. Rev. D. 72, (2005) S3 search complete Under internal review 0.09 yr of data Rate < 47 per year per Milky Way like galaxy; 0.04 yr data, 1.27 Milky Ways signal to noise ratio squared ~3 Milky Way like galaxies S4 search complete Under internal review 0.05 yr of data ~24 Milky Way like galaxies 15

16 Binary Neutron Stars S5 Search First three months of S5 data is analyzed Horizon distance S2 Horizon Distance 1.5 Mpc Distance to Msun optimally oriented & located binary at SNR=8 H1: 25 Mpc L1: 21 Mpc H2: 10 Mpc 16

Binary Black Holes S2 Observational Result S3 search complete Log cum. no. of events Phys. Rev. D. 73, 062001 (2006) Under internal review 0.

17 Binary Black Holes S2 Observational Result S3 search complete Log cum. no. of events Phys. Rev. D. 73, (2006) Under internal review 0.09 yr of data S4 search complete Rate < 38 per year per Milky Way like galaxy signal to noise ratio squared 5 Milky Way like galaxies for 5+5 Msuns Under internal review 0.05 yr of data 150 Milky Way like galaxies for 5+5 Msuns17

18 Binary Black Holes S5 Search binary neutron star horizon distance 3 months of S5 analyzed Horizon distance versus mass for BBH Average over run 130Mpc 1 sigma variation binary black hole horizon distance Image: R. Powell 18

spacetime geometry Spinning neutron stars Isolated neutron stars with

19 Astrophysical sources of gravitational waves Compact binaries Black holes & neutron stars Inspiral and merger Probe internal structure, populations, & spacetime geometry Spinning neutron stars Isolated neutron stars with mountains or wobbles Low mass x ray binaries Probe internal structure and populations 19

Search for waves from known pulsars Gravitational wave amplitude S2 Results reported in Physical Review Letters 94 181103 (2005) 04/11/2006 Pulsars for which the ephemeris is

20 Search for waves from known pulsars Gravitational wave amplitude S2 Results reported in Physical Review Letters (2005) 04/11/2006 Pulsars for which the ephemeris is known from EM observations In S2 ~2x known isolated pulsars targeted Spindown limit Frequency (Hz) APS Meeting, April 2006 assume all angular momentum radiated to 20 GW

21 Known pulsars S5 preliminary Gravitational wave amplitude 32 known isolated, 44 in binaries, 30 in globular clusters Lowest ellipticity upper limit: PSR J (fgw = 405.6Hz, r = 0.25kpc) ellipticity = 4.0x10 7 ~2x10 25 Frequency (Hz) 04/11/2006 APS Meeting, April

22 To participate, sign up at S3 results: No evidence of pulsars S4 search Post processing underway 04/11/2006 Matched ﬁltering for continuous GWs All sky, all frequency search is computationally limited Aiming at detection, not upper limits Public outreach distributed computing APS Meeting, April

23 Conclusions LIGO results are starting to come out Have presented only a few results in this talk Other ongoing activities: Continuous waves: known pulsars in x ray binaries; deep area searches; coherent long time searches Compact binaries: ringdown searches; inspiral merger ringdown; short hard GRBs. Stochastic: directional Bursts: galactic center search, suppressing search; cosmic string search; correlated noise for H1 targeted supernova searches H2; S4 L1 ALLEGRO (bar detector) search APS Meeting, April /11/2006

Searching for gravitational waves. with LIGO detectors

Werner Berger, ZIB, AEI, CCT Searching for gravitational waves LIGO Hanford with LIGO detectors Gabriela González Louisiana State University On behalf of the LIGO Scientific Collaboration KITP Colloquium,