Gravitational-wave (GW) detectors in the
nexus of multi-messenger astrophysics
Isabel Leonor (University of Oregon)
For the LIGO Scientific Collaboration
and the Virgo Collaboration
LIGO-G0900682
Overview: LIGO-Virgo is fully engaged in
multi-messenger astrophysics
optical
gamma rays,
x-rays
neutrinos
radio
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
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The GRB sample for the LIGO-Virgo
S5/VSR1 run
GRB triggers were mostly from Swift;
some were from IPN3, INTEGRAL, HETE-2
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during S6/VSR2 run, GRB
triggers will be mostly from
Fermi+Swift
 factor of ~3 increase in
trigger rate
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
Virgo
average antenna factor
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
LIGO Hanford
average antenna factor
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Search for gravitational-wave burst (GWB)
counterparts to GRBs (S5/VSR1 run)
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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
EGW 
 2c 3
G
2
D 2 f 02 hrss
results for 137 GRBs
(paper due soon)
EGW  0.01 M sun , f 0  150 Hz
1/ 2
 EGW 

 D ~ 15 
 0.01 M sun 
July 15, 2009 SLAC
Mpc
3
1 / 3
V  Dreach
 hIFO
TeV Particle Astrophysics, LIGO-G0900682
for Advanced LIGO-Virgo
D ~ 150 Mpc
4
Search for GW inspiral signals from GRBs
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used to search for GW counterpart
to short GRBs
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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
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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)
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
NS-NS merger simulation
Price and Rosswog
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GRB 070201: In M31 or beyond?
GRB or soft gamma repeater (SGR)?
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(arXiv:0712.1502)
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)
July 15, 2009 SLAC
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Search for GW bursts coincident with
soft gamma repeater (SGR) bursts
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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 an
SGR storm (SGR 1900+14)
30 seconds
SGR 1900+14 lightcurve
(Mar 29, 2006)
from
Swift-BAT telescope
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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)
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
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Search for periodic GW signals from
known pulsars
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target signal: monochromatic
signals emitted by pulsars
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most likely mechanism for
production of detectable GW is
small distortions of the NS shape
away from axisymmetry
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search at GW frequency twice the
pulsar rotation frequency
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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
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S5 best limit: h0=2.3E-26 at the
sweet spot (paper due soon)
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best ellipticity limit of 7E-8
Jodrell Bank
Parkes Telescope
Green Bank
116 known pulsars 95% upper limits (preliminary)
Crab pulsar: beating the spin-down limit
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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)
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using entire S5 data gives UL
which beats spin-down limit by ~7
Jodrell Bank
Credits:
X-ray:
NASA/CXC/ASU/
J. Hester et al.;
Optical:
NASA/HST/ASU/
J. Hester et al.
Swift target of opportunity (ToO)
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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
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
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Swift target of opportunity (ToO)
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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
July 15, 2009 SLAC
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LOOC UP
Locating and Observing Optical Counterparts to
Unmodeled Pulses in gravitational waves
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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.)
July 15, 2009 SLAC
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Gravitational waves and neutrinos (nascent collaborations)
LVD
Borexino
Super-K
IceCube
ANTARES
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Supernova early warning system (SNEWS)
http://snews.bnl.gov
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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
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
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Estimates of Galactic and nearby
core-collapse supernova rate
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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
July 15, 2009 SLAC
Ando, S. et al. 2005, PRL, 95, 171101
TeV Particle Astrophysics, LIGO-G0900682
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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 corecollapse 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
 improvement in sensitivity
EGW 
July 15, 2009 SLAC
G
2
153 Hz
D 2 f 02 hrss
LMC
Energy into GW (solar masses)
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 2c 3
Models for GW emission
(from Ott, C. 2009, CQG, 26, 063001)
A: PNS pulsations
B: rotational instability
C: rotating collapse and bounce
D: convection and SASI
TeV Particle Astrophysics, LIGO-G0900682
Andromeda
Distance (kpc)
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Joint search could benefit
neutrino search as well
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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
July 15, 2009 SLAC
Probability of satisfying criterion
Detection probability
LMC
Andromeda
standard criterion
relaxed criterion
TeV Particle Astrophysics, LIGO-G0900682
Distance to supernova (kpc)
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Gravitational waves and
high-energy neutrinos
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ANTARES (Mediterranean Sea)
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)
IceCube (South Pole)
July 15, 2009 SLAC
TeV Particle Astrophysics, LIGO-G0900682
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Other current or future multi-messenger
activities
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analysis of Swift data to extract sub-threshold events (possible
GRBs) which can increase GRB sample which serve as triggers to
GW analysis
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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
…
July 15, 2009 SLAC
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Summary
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LIGO and Virgo are fully engaged in multi-messenger astrophysics
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These multi-messenger analyses continue to be pursued during the
current S6/VSR2 run
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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
July 15, 2009 SLAC
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