LIGO­G060199­00­Z

LIGO Observational Results

Patrick BradyUniversity of Wisconsin­Milwaukee

on behalf of

LIGO Scientific Collaboration

08/30/2006 TEV II, August 2006 2LIGO­G060199­00­Z

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

08/30/2006 TEV II, August 2006 3LIGO­G060199­00­Z

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

08/30/2006 TEV II, August 2006 4LIGO­G060199­00­Z

Search Method: Time­frequency decompositions

Noise event: triggers and spectrogram

Simulated injection in hardware

Requires coincidence between at leasttwo interferometers & detailed examinationof instrumental & environmental behavior

08/30/2006 TEV II, August 2006 5LIGO­G060199­00­Z

Detection Efficiency Evaluate efficiency by adding simulated GW

bursts to the data.– Example waveform

Central Frequency

Dete

ctio

n Ef

ficie

ncy

S4

S5 sensitivity: minimum detectable in band energy in GW– EGW > 1 M

⊙ @ 75 Mpc

– EGW > 0.05 M⊙ @ 15 Mpc (Virgo cluster)

08/30/2006 TEV II, August 2006 6LIGO­G060199­00­Z

S2

S1

S4 projected

Excluded 90% CL

S5 projected

Rate

Lim

it (e

vent

s/da

y)

Upper Limits No GW bursts detected through S4

– set limit on rate vs signal strength.

Lower amplitude limits from lower detector noise

Lower rate limits from

longer observation

times

08/30/2006 TEV II, August 2006 7LIGO­G060199­00­Z

Triggered Searches Follow up astronomical triggers, particularly gamma­ray

bursts54 GRB

tests

S2/S3/S4 result

– 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

08/30/2006 TEV II, August 2006 8LIGO­G060199­00­Z

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

08/30/2006 TEV II, August 2006 9LIGO­G060199­00­Z

Signals from the Early Universe

cosmic gravitational­wave background (10­22s)

cosmic microwave background (10+12s)

Cosmological GWs in the LIGO band (100 Hz) today were produced 10­22s after the big bang.

Their detection would be very interesting!

08/30/2006 TEV II, August 2006 10LIGO­G060199­00­Z

Y = df -

x 1*(f) g(f)WGW(f)

N f 3P1(f)P2(f) x 2(f)

Procedure

detector noise spectra

Test ΩGW(f) = Ωα(f/100Hz)α. Most sensitivity from 50­150 Hz band (LHO­LLO).

“Overlap Reduction Function”(determined by network geometry)

frequency (Hz)

γ(f)

Search: cross­correlate datastreams x1, x2. Optimal

statistic Y for all­sky search is:

08/30/2006 TEV II, August 2006 11LIGO­G060199­00­Z

­16 ­14 ­12 ­10 ­8 ­6 ­4 ­2 0 2 4 6 8

­14

­12

­10

­8

­6

­4

­2

0

Log (f [Hz])

Log(Ω

0)

­18 10

Inflation

Slow­roll

Cosmic strings

Pre­big bang model

EW or SUSY Phase transition

Cyclic model

CMB

PulsarTiming

BB Nucleo­synthesis

Initial LIGO, 1 yr dataExpected Sensitivity

~ 4x10­6

Advanced LIGO, 1 yr dataExpected Sensitivity

~ 1x10­9

LIGO S1: Ω0 < 44

PRD 69 122004 (2004)

LIGO S3: Ω0 < 8.4x10­4

PRL 95 221101 (2005)

Predictions and Limits

H0 = 72 km/s/Mpc

08/30/2006 TEV II, August 2006 12LIGO­G060199­00­Z

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

– Low­mass x­ray binaries– Probe internal structure and

populations

08/30/2006 TEV II, August 2006 13LIGO­G060199­00­Z

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.

08/30/2006 TEV II, August 2006 14LIGO­G060199­00­Z

Target Sources

0.1 1 3 10

0.1

Component Mass, M⊙

1

3

10

Com

pone

nt M

ass,

M⊙

PBHS2 – S5

BNS S1 – S5

BBH: S2 – S5Ringdown: S4 – S5

Coincidence with burst search

NS/BHspin important

S3 – S5

Binary Black Hole– Theory estimates

upper bound of 1/year for LIGO during S5

Binary Neutron Star– Theory estimates

upper bound of 1/3 year for LIGO during S5

08/30/2006 TEV II, August 2006 15LIGO­G060199­00­Z

Binary Neutron Starscu

mul

ative

num

ber o

f eve

nts

signal­to­noise ratio squared

S2 Observational Result

Phys. Rev. D. 72, 082001 (2005)

S3 search complete– Under internal review– 0.09 yr of data– ~3 Milky­Way like

galaxies S4 search complete

– Under internal review– 0.05 yr of data– ~24 Milky­Way like

galaxies

Rate < 47 per year perMilky­Way­like galaxy;

0.04 yr data, 1.27 Milky­Ways

08/30/2006 TEV II, August 2006 16LIGO­G060199­00­Z

Horizon distance– Distance to 1.4+1.4 Msun

optimally oriented & located binary at SNR=8

Binary Neutron StarsS5 Search

First three months of S5 data is analyzed

S2 Horizon Distance

1.5 Mpc

H1: 25 Mpc

L1: 21 Mpc

H2: 10 Mpc

08/30/2006 TEV II, August 2006 17LIGO­G060199­00­Z

Binary Black Holes

signal­to­noise ratio squared

Rate < 38 per year perMilky­Way­like galaxy

S2 Observational Result

Phys. Rev. D. 73, 062001 (2006)

S3 search complete– Under internal review– 0.09 yr of data– 5 Milky­Way like galaxies

for 5+5 Msuns S4 search complete

– Under internal review– 0.05 yr of data– 150 Milky­Way like

galaxies for 5+5 Msuns

Log|

cum

. no.

of e

vent

s |

08/30/2006 TEV II, August 2006 18LIGO­G060199­00­Z

Binary Black HolesS5 Search

Image: R. Powell

binary black holehorizon distance

3 months of S5 analyzed Horizon distance versus

mass for BBHAverage over run

130Mpc

1 sigma variation

binary neutron star horizon distance

08/30/2006 TEV II, August 2006 19LIGO­G060199­00­Z

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

– Low­mass x­ray binaries– Probe internal structure and

populations

04/11/2006 APS Meeting, April 2006 20LIGO­G060199­00­Z

Search for waves from known pulsars

S2 Results reported inPhysical Review Letters 94 181103 (2005)

Pulsars for which the ephemeris is known from EM observations

In S2– 28 known isolated

pulsars targeted Spindown limit

– assume all angular momentum radiated to GW

Frequency (Hz)Gra

vitat

iona

l­wav

e am

plitu

de

~2x10­24

04/11/2006 APS Meeting, April 2006 21LIGO­G060199­00­Z

Known pulsarsS5 preliminary

32 known isolated, 44 in binaries, 30 in globular clusters

Lowest ellipticity upper limit:PSR J2124­3358

(fgw = 405.6Hz, r = 0.25kpc) ellipticity = 4.0x10­7

Frequency (Hz)

Gra

vitat

iona

l­wav

e am

plitu

de

~2x10­25

04/11/2006 APS Meeting, April 2006 22LIGO­G060199­00­Z

Einstein@Home Matched­filtering for

continuous GWs All­sky, all­frequency

search is computationally limited

Aiming at detection, not upper limits

Public outreach distributed computing

To participate, sign up at http://www.physics2005.org

S3 results:– No evidence of pulsars

S4 search– Post­processing underway

04/11/2006 APS Meeting, April 2006 23LIGO­G060199­00­Z

Conclusions LIGO results are starting

to come out Have presented only a

few results in this talk Other ongoing activities:

– Stochastic: directional search, suppressing correlated noise for H1­H2; S4 L1­ALLEGRO (bar detector) search

Continuous waves: known pulsars in x­ray binaries; deep area searches; coherent long­time searches

Compact binaries: ringdown searches; inspiral­merger­ringdown; short­hard GRBs.

Bursts: galactic center search; cosmic string search; targeted supernova searches