gravitational-wave (gw) detectors in the nexus of multi-messenger astrophysics

Gravitational-wave (GW) detectors in the nexus of multi-messenger astrophysics

Isabel Leonor (University of Oregon)

For the LIGO Scientific Collaboration

and the Virgo CollaborationLIGO-G0900682

optical

radio

gamma rays,x-rays

neutrinos

Overview: LIGO-Virgo is fully engaged inmulti-messenger astrophysics

July 15, 2009 SLAC TeV Particle Astrophysics, LIGO-G0900682 2

The GRB sample for the LIGO-VirgoS5/VSR1 run

212 GRB triggers from Nov. 4, 2005 to Oct. 1, 2007

~70% with double-IFO coincidence LIGO data

~45% with triple-IFO coincidence LIGO data

~15% short-duration GRBs

~25% with redshift

during S6/VSR2 run, GRB triggers will be mostly from Fermi+Swift

factor of ~3 increase in trigger rate


GRB triggers were mostly from Swift;some were from IPN3, INTEGRAL, HETE-2

LIGO

Hanford

average a

ntenna factor

Virg

o averag

e ante

nna factor

Search for gravitational-wave burst (GWB)counterparts to GRBs (S5/VSR1 run)

used to search for GW counterpart to both long and short GRBs

burst search is model-independent targets GW signals less than ~few

seconds fully coherent search which

cross-correlates data streams from different interferometers

set 90% upper limits on strain for each GRB

assuming energy emitted in GW

July 15, 2009 SLAC TeV Particle Astrophysics, LIGO-G0900682

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Hz 150 , 01.0 0sunGW fME

Mpc 01.0

15~2/1

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GW

M

ED

4

3/1IFO

3reach

hDV for Advanced LIGO-VirgoD ~ 150 Mpc

results for 137 GRBs(paper due soon)

Search for GW inspiral signals from GRBs

used to search for GW counterpart to short GRBs

there is evidence that short GRBs are nearer

search makes use of inspiral templates

target GW inspiral signals from coalescing masses in the range 1 M < m1 < 3 M, 1 M < m2 < 40 M

during S5 run, inspiral search range for NS merger event was ~15 Mpc (SNR=8)

for S5 run, 21 short GRBs have been analyzed; no candidate events found

set lower limit on distance for each GRB (paper due out soon)


NS-NS merger simulationPrice and Rosswog

GRB 070201: In M31 or beyond?GRB or soft gamma repeater (SGR)?

short GRB whose position error box overlapped with spiral arms of Andromeda galaxy (M31, ~770 kpc)

occurred during LIGO S5 run; two Hanford interferometers were in science mode

inspiral search analysis excludes binary merger event at M31 with >99% confidence; larger distances also excluded with high confidence

burst search analysis gives upper limits on GW energy released; these limits do not exclude a model of a soft gamma repeater in M31(ApJ, 2008, 681, 1419)


(arXiv:0712.1502)

Search for GW bursts coincident with soft gamma repeater (SGR) bursts

SGRs thought to be highly magnetized neutron stars (~1E+15 G)

most observed SGRs are Galactic SGR bursts from crustal deformations

and catastrophic cracking may be accompanied by GW burst emission

search for excess power from GW burst relies on SGR lightcurves from Interplanetary Network (IPN3), including Swift, Konus-Wind, etc.

191 bursts from SGR 1806-20 and SGR 1900+14 have been analyzed for coincident GW emission using LIGO

some of the upper limits set on GW energy emission already explore some SGR models

90% UL on energy of GW emission coincident with 215 SGR bursts

(PRL, 2008, 101, 211102)

Robert Mallozzi (UAH, MSFC)

Search for GW burst emission from anSGR storm (SGR 1900+14)

assume GW signal accompanies each storm episode

“stacking” power from different storm episodes leads to increased GW search sensitivity requires precise timing from SGR lightcurve for start time of each storm episode

resulting upper limits on GW energy emission ~order of magnitude lower than non-stacked analysis(arXiv:0905.0005)


SGR 1900+14 lightcurve (Mar 29, 2006)

fromSwift-BAT telescope

30 seconds

Search for periodic GW signals from known pulsars

116 known pulsars 95% upper limits (preliminary)

target signal: monochromatic signals emitted by pulsars

most likely mechanism for production of detectable GW is small distortions of the NS shape away from axisymmetry

search at GW frequency twice the pulsar rotation frequency

search method makes use of a signal template for each pulsar requires updated ephemeris data to model phase evolution of pulsar signal requires collaboration with radio pulsar astronomers

S5 best limit: h0=2.3E-26 at the sweet spot (paper due soon)

best ellipticity limit of 7E-8

Jodrell Bank Parkes TelescopeGreen Bank

Crab pulsar: beating the spin-down limit spin-down limit assumes all the

pulsars rotational energy loss is radiated by gravitational wave

we know some energy is emitted electromagnetically and is powering the expansion of the Crab nebula

this is poorly constrained and allows room for gravitational wave emission

search method depends on data from Jodrell Bank Crab Pulsar monthly ephemeris to track the phase

using first nine months of LIGO S5 data, obtain 95% upper limit on strain amplitude of h0=2.7E-25 lower than classical spin-down limit by a factor of ~5 (ApJ, 2008, 683, L45)

using entire S5 data gives UL which beats spin-down limit by ~7

Credits: X-ray:

NASA/CXC/ASU/J. Hester et al.;

Optical: NASA/HST/ASU/

J. Hester et al.Jodrell Bank

Swift target of opportunity (ToO)

during S6/VSR2, possible GW candidates from all-sky burst and inspiral searches will be verified by requesting electromagnetic follow-up observations

X-ray follow-up will be requested from Swift

LIGO-Virgo error box will be ~few degrees

verification of astrophysical object by an EM counterpart will further probe nature of object

anticipates era of regular GW detections using more sensitive detectors, i.e. Advanced LIGO, Advanced Virgo


LOOC UP

for S6/VSR2 run, position information of GW triggers from all-sky burst search will be sent to available optical telescopes via automated interface

imaging/follow-up will be requested from telescopes

expect initial latency of ~30-60 minutes from GW trigger to imaging

LOOC UP currently pursuing MOU’s with telescopes (SkyMapper, ROTSE, TAROT, etc.)


Locating and Observing Optical Counterparts to Unmodeled Pulses in gravitational waves

Gravitational waves and neutrinos (nascent collaborations)


LVD Borexino Super-K

IceCube

ANTARES

Supernova early warning system (SNEWS)http://snews.bnl.gov


alert system which would send out notification of high-confidence SN to astronomical community a few minutes after detection of neutrino burst by multiple detectors

LIGO-Virgo is signed up to get these alerts in the control rooms

low-latency search for a GW signal coincident with a SNEWS trigger is planned for the LIGO-Virgo S6/VSR2 run

there is a proposed joint GW-neutrino search which will complement the existing infrastructure and procedures which are in place in the event of a SNEWS alert

Estimates of Galactic and nearby core-collapse supernova rate

estimated Galactic rate is a few (~3) per century

estimated rate in Local Group (out to ~1 Mpc) ~twice the Galactic rate

~1 per year out to the Virgo cluster observations indicate that the

true nearby SN core-collapse rates could be higher than these estimates (e.g. ~3 times higher, using observed SN in 2002-2005)

electromagnetically dark or obscured SN would also bring uncertainties to these rates


Ando, S. et al. 2005, PRL, 95, 171101

LIGO sensitivity and expected improvement with joint neutrino search

in contrast to neutrino signal, energy emitted as GW radiation is expected to be small

currently, there are large uncertainties in models of core-collapse SN, e.g. simulations have difficulty making a SN explode

like neutrino signal, GW signal would probe the innermost region of SN core

requiring coincidence of GW and neutrino signals to within a short time window of ~few seconds would allow lower detection thresholds


2rss

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GW hfDG

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improvement in sensitivity

Models for GW emission (from Ott, C. 2009, CQG, 26, 063001)A: PNS pulsationsB: rotational instabilityC: rotating collapse and bounceD: convection and SASI

En

erg

y in

to G

W (

sola

r m

asse

s)

LMC Andromeda

153 Hz

Distance (kpc)

Joint search could benefit neutrino search as well


criterion for neutrino search can be relaxed

example: for Super-K distant SN search, criterion is at least 2 neutrino events per 20 seconds and high energy threshold of 17 MeV

if coincidence with GW signal is used, then criterion can be relaxed to a single neutrino event; odds will increase that distant core-collapse will satisfy this criterion

energy threshold could also be lowered

Pro

bab

ility

of

sati

sfyi

ng

cri

teri

on

Distance to supernova (kpc)

LMC Andromeda

Detection probability

standard criterionrelaxed criterion

Gravitational waves and high-energy neutrinos

currently a collaborative effort between LIGO, Virgo, IceCube, ANTARES

joint GW and high-energy neutrino search will lower background rate

both GW and high-energy neutrino signals travel long distances without absorption

possible sources: long and short GRBs, low-luminosity GRBs, failed GRBs, soft gamma repeaters

overlapping GW and neutrino data is available from past runs (S5/VSR1) and will be available from future runs (S6/VSR2 and beyond)

July 15, 2009 SLAC 19TeV Particle Astrophysics, LIGO-G0900682

ANTARES (Mediterranean Sea)

IceCube (South Pole)

Other current or future multi-messenger activities

analysis of Swift data to extract sub-threshold events (possible GRBs) which can increase GRB sample which serve as triggers to GW analysis

analysis is currently ongoing (E. Harstad, University of Oregon) search for GW bursts coincident with pulsar glitches search for GW signal associated with RXTE observations of Sco X-

1 radio-triggered searches for GW bursts …


Summary

LIGO and Virgo are fully engaged in multi-messenger astrophysics

These multi-messenger analyses continue to be pursued during the current S6/VSR2 run

These activities and the nascent collaborations serve as a strong foundation for analyses of future, more sensitive data as an era of regular GW detections is anticipated with Advanced LIGO-Virgo


gravitational-wave (gw) detectors in the nexus of multi-messenger astrophysics

Documents

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