from initial to advanced gravitational wave interferometers: results, challenges and prospects

S.Klimenko, December 18, 2010, Miami, LIGO-G1001097-v3

Credit: AEI, CCT, LSU

From Initial to Advancedgravitational wave interferometers:results, challenges and prospects.

Sergey Klimenko, University of Floridafor the LIGO and Virgo collaborations


Gravitational Waves

after a decade of experiments with the initial (1G) GW interferometers, the advanced (2G) detectors are targeting detection of GWs in ~2016 – 100 years after their prediction.

J.Weber: ”When I decided to search for gravitational waves some 14 years ago, most physicists applauded our courage@, but felt that success – detection of gravitational radiation – would require a century of experimental work.” (Popular Science May 1972)

@ W.Churchill: “Courage is going from failure to failure without losing enthusiasm”

space-time perturbations propagating at the speed of light predicted by A.Einstein in 1916 as part of his theory of General Relativity


Gravitational Waves: the evidence

PSR 1913 + 16 Neutron Binary SystemSeparated by 106miles, m1 = 1.4m; m2 = 1.36m;

Prediction from general relativity• spiral in by 3 mm/orbit• merge in 300 million years

Emission of gravitational waves

time of periastron relative to that expected if the orbital separation

remained constant.

Hulse & Taylor


GW Detectors

LIGO, VIRGO, GEO, TAMA:breakthrough in the GW experiment

Interferometerswideband (~10000 Hz)

ALLEGRO, AURIGA, EXPLORER, NAUTILUS,

NIOBE, …

Barsnarrowband (~1Hz)

recent improvements (~10Hz)

UF graduate student Kate Dooley inspecting a LIGO optic.J.Weber working on the bar

1968 2008


Sensitivity of 1G Interferometers

Hz

1 102

4000

)()( 23

m

fLfSstrain noise:

fermi 10~100)( 3 HzfL


LIGO Observatory

Initial LIGO detectors (1G) were in operation for a decade6 data taking runs (~1.5 years of 2D live time)reached its design sensitivity during the S5 run: 2005-2007 Virgo detector joined in May 2007 (VSR1 run)run enhanced configuration during the s6 run: 2009 – 2010decommissioned in October 2010

started to constrain source models (analysis of data continues)paved road for aLIGO 2G detectorsestablished conceptually new GW data analysisbegan integration of GW experiment and astronomy

Livingston, LA (LLO)L1: 4km x 4km

Hanford, WA (LHO) H1: 4km x 4km H2: 2km x 2km


Gravitational Wave Sources

and other violent astrophysical sources..

Credit: Chandra X-ray Observatory

Casey Reed, Penn State

NS-NS

Credit: AEI, CCT, LSU

binary neutron stars

binary black holespulsars

supernovae

gamma ray bursts

soft gamma repeaters


Compact Binary Coalescence: NS-NS

110

1-3 Ly 108.7

LTC

1rate

PRD 82 (2010) 102001

S5

NS-NS – LIGO standard candle (1G horizon ~30Mpc)) large expected signal, inspiral in the sweet spot (100-300Hz) challenges: get physics at merger phase (~1.5kHz)

CL – cumulative luminosity (370L10) T – observation time (~1 year)

measured rate limit: <3.2 / year: expected rates: ~0.01 / year

inspiral: PN GR merger: NR GR BH ringdown

L10

= 1010 L,B

(1 Milky Way = 1.7 L

10)

LTC

1rate


Black Holes


BH binary coalescence: BH-BH & BH-NS

BH searches low mass BH & NS (<25Mo) search with inspiral templates high mass BH-BH (25-100Mo) search with IMR templates massive BH-BH (100-500Mo) burst searches

high mass CBC (>25Mo) are better detected via their merger and ring-down waves (in progress). Challenges: need merger waveforms (Numerical Relativity calculations) background due to non-stationary detector noise

MM

mergeroHzf 20

205

M<20Mo

Background: S5/VSR1 burst search

eve

nt s

tren

gth


Low Mass CBC BH search S5/VSR1 run (T~1year): PRD 82 (2010) 102001 Measure rate limits:

Expected rates

110

1-5-8 Ly )10510(3 :NSBH

110

1-5-8 Ly )10210(1 :BHBH

LTC

1rate

NS(1.35Mo)-BH

BH-BH

BH(5Mo)-NS: CL = 1600L10

BH(5Mo)-BH(5Mo): CL = 8300L10

110

1-4 Ly 104.4

110

1-3 Ly 102.2

CQG. 27 (2010) 173001

All-Sky Burst Searches

model independent, however sensitive to a wide class of sources: binary mergers, SN, SGR,..

use ad-hoc waveforms (Sine-Gaussian, Gaussian, etc.) to determine detection sensitivity

Challenges: affected by detector glitches need smart network search algorithms and very detail understanding of the detector noise

Sine-Gaussian waveforms, Q=8.9

PRD 72(2005) 062001CQG 24(2007) 5343-5369

CQG 25(2008) 245008


Supernova

Karachentsev et al. 2004;Cappellaro et al. 1999

GW from supernova Several Core-Collapse SN

Mechanisms Direct “live” information

from the supernova engine.

1/50 yr - Milky Way

258 1010 cMEGW

Ott, et al.


Mass equivalent sensitivity

220

32

)2(4 rssGW hfG

crE

strain sensitivity can be converted to energy sensitivity assuming isotropic GW emission

Capable to detect burst sources out to Virgo cluster if EGW is few % of Mo

For lower energy output (like SNs, which also produce HF signals) need advanced detectors to see beyond our Galaxy

16Mpc

10kpc


short GRB070201 short GRB070201 no gravitational waves detected

APJ 681 (2008) 1419

25%

50%

75%

90%

DM31≈770 kpc

Sky location consistent with Andromeda (M31)Possible progenitors:NS-NS or BH-NS merger Soft Gamma Repeater

• Inspiral search:excludes binary progenitor in Andromeda at >99% confidence levelExclusion of merger at larger distances

•Burst search:Cannot exclude a Soft Gamma Repeater (SGR) at M31 distanceUpper limit: EGW<8x1050

ergs (<4x10-4 Moc2)

more GRB results: APJ 715 (2010) 1438

search for GWs from 137 GRBs in S5


GWs from 116 known pulsars

APJ. 713 (2010) 671 limits on GW amplitude

S3/S4

S5

4

2216

rc

GIh zzGW

10-25


Beating the Crab Pulsar Spin Down Limit

•Young and rapidly spinning down

•GW frequency 59.6 Hz

Experimental limits

•GW strength:

h(95%CL) < 2.0 x 10-25

the spin down limit (assuming restricted priors)

• ellipticity limit: < 1.0 x 10-4

• GW energy upper limit: < 2% of radiated energy is in GWs

Astrophys. J. 713 (2010) 671

zz

yyxx

I

II


Stochastic Background

LIGO S5 result:6.9 x 10-6

Nature., V460: 990 (2009).


Multimessenger Astronomy

observation and measurement of the same astrophysical event by different experiments better confidence of GW event extract physics of source engine

Externally triggered strategy routinely used by LIGO

Look-Up strategy close integration with astronomy:

search for EM counterpart with optical and radio telescopes

need low latency (few min) source localization from GW detectors

rely on source reconstruction In 2009-2010 LIGO and Virgo carried

out first EM followup experiments analysis in progress


Challenges of GW reconstruction

If detection of GW signals is hard, the reconstruction even harder and not really addressed yet.

•incomplete or no source models

•dependence on antenna patterns & detector noise

•dependence on GW waveforms and polarization state

•reconstruction bias due to algorithmic assumptions

•reconstruction bias due to calibration errors

•high computational cost

•….there are many ways to get it wrongneed smart algorithmseventually need more detectors


Source localization method

hFhFhdet

, Based on triangulation (1,2,3,..)

3 or more sites

Coupled to reconstruction of GW waveforms coherent analysis of data from all detectors in the network.

2

13

error regionProbability map


Antenna patterns & noise

dtthhhfhfSNR )( , 2,

2,

2222

,..., , ,...,1

1

1

1

K

K

K

K FFFF ff

network sensitivity:

network SNR

detectors with small fk do not contribute to reconstruction effectively deal with 2 detector network lose triangulation need more than 3 sites for robust reconstruction

22 FF

LIGO

Virgo


Waveforms & polarization

Simulated signal (SG235Q9)with linear polarization

simulated signal (WNB 250

Hz)with two random polarizations

F V1, L1, H1

0~when F

accu

racy,

deg

rees

For linearly polarized signal effectively lose a detector

For signals with random polarization, recover reconstruction due to the 2nd polarization

This effect strongly depends on the sky location

additional 4th site solves the problem

2G (advanced) detectors

x10 better sensitivity than for 1G aLIGO Is being constructed start operation in 2014-2015 aVirgo will emerge in about the same time after a series of

upgrades which are in progress. hopefully LIGO-A and LCGT will be constructed huge

increase in scientific output, make GW astronomy a reality.

aLIGO LCGTaVIRGO

LIGO-Australia(LIGO-A)

LIGO goes south? Plans for relocation of one H detector to Australia, Gingin

5-10 times better sky resolution – compatible with FOV of telescopes conditional approval from NSF

LHHV

LHVA

network SNR

Err

or

an

gle

in

deg

rees

longitude

lati

tud

e

Physics Today, Dec, 2010committee report at

https://dcc.ligo.org/public/0011/T1000251/001/

LHHVLHVA


Class. Quantum Grav. 27 (2010) 173001

2G Astronomical Reach

x10 better amplitude sensitivity

x1000 rate=(reach)3

BH-BH20-2000 y-1

NS-NS20-200

y-1

SN0.02-0.5 y-1

CQG. 27 (2010) 173001

from initial to advanced gravitational wave interferometers: results, challenges and prospects

Documents

g gw interferometers

g detectors

g horizon

virgo detector

ligo optic

ns ligo standard candle

g interferometersstrain

expected ratesbh5mons