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-G

optical radio gamma rays, x-rays neutrinos Overview: LIGO-Virgo is fully engaged in multi-messenger astrophysics July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G

The GRB sample for the LIGO-Virgo S5/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 July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G GRB triggers were mostly from Swift; some were from IPN3, INTEGRAL, HETE-2 LIGO Hanford average antenna factor Virgo average antenna 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 SLACTeV Particle Astrophysics, LIGO-G for Advanced LIGO-Virgo D ~ 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  < m 1 < 3 M , 1 M  < m 2 < 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) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G NS-NS merger simulation Price and Rosswog

GRB : 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) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G (arXiv: )

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 and SGR 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, ) Robert Mallozzi (UAH, MSFC)

Search for GW burst emission from an SGR storm (SGR )  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: ) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G SGR lightcurve (Mar 29, 2006) from Swift-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: h 0 =2.3E-26 at the sweet spot (paper due soon)  best ellipticity limit of 7E-8 Jodrell BankParkes Telescope Green 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 h 0 =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 July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G

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 July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G

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.) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G Locating and Observing Optical Counterparts to Unmodeled Pulses in gravitational waves

Gravitational waves and neutrinos (nascent collaborations) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G LVD Borexino Super-K IceCube ANTARES

Supernova early warning system (SNEWS) July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G  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 )  electromagnetically dark or obscured SN would also bring uncertainties to these rates July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G Ando, S. et al. 2005, PRL, 95,

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 July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G  improvement in sensitivity Models for GW emission (from Ott, C. 2009, CQG, 26, ) A: PNS pulsations B: rotational instability C: rotating collapse and bounce D: convection and SASI Energy into GW (solar masses) LMC Andromeda 153 Hz Distance (kpc)

Joint search could benefit neutrino search as well July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G  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 Probability of satisfying criterion Distance to supernova (kpc) LMCAndromeda Detection probability standard criterion relaxed 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 SLAC19TeV Particle Astrophysics, LIGO-G 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  … July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G

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 July 15, 2009 SLACTeV Particle Astrophysics, LIGO-G