Gravitational Wave – GRB connections?

1. Gravitational Wave – GRB connections? Jim Hough Institute for Gravitational Research University of Glasgow Royal Society September 2006

2. ‘Gravitational Waves’ • Produced by violent acceleration of mass in: • neutron star binary coalescences • black hole formation and interactions • cosmic string vibrations in the early universe • and in less violent events: • pulsars • binary stars • Gravitational waves • ‘ripples in the curvature of spacetime’ that carry information about changing gravitational fields – or fluctuating strains in space of amplitude h where

3. Sources – the gravitational wave spectrum Gravity gradient wall ADVANCED GROUND - BASED DETECTORS

4. “Indirect”detection of gravitational waves Evidence for gravitational waves PSR 1913+16

5. Detection of Gravitational waves Consider the effect of a wave on a ring of particles : One cycle Fabry-Perot/Michelson Interferometer Gravitational waves have very weak effect: Expect movements of less than a trillionth of the wavelength of light (10-18 m) over 4km

6. GW detector network

7. GEO 600 600m

8. Gravitational wave network sensitivity Gravitational wave amplitude h (/Hz) Frequency (Hz)

9. LIGO now at design sensitivity

10. Science data runs to date • Since Autumn 2001 GEO and LIGO have completed 4 science runs • Analysis completed for S1/2 and (most) papers published; • For S3/4 analysis – 2 papers published and many more in preparation • Some runs done in coincidence with TAMA and bars (Allegro) • LIGO now at design sensitivity • ‘Upper Limits’ have been set for a range of signals • Coalescing binaries • Pulsars • Bursts (including GRBs) • Stochastic background • >15 major papers published or in press since 2004 (work from a collaboration (LSC) of more than 400 scientists) S5: started on 4th Nov. 2005 at Hanford (LLO a few weeks later) - GEO joined initially for overnight data taking, then 24/7 • 18 months data taking in coincidence

11. Gravitational Waves from compact binaries Estimates give upper bound of 1/3 yr in LIGO S5

12. binary neutron star max. distance LIGO Range Image: R. Powell Binary Coalescence Sources & Science: binary black hole max.distance

13. Burst sources Burst Sources: • No gravitational wave bursts detected during S1, S2, S3, and S4; upper limits set through injection of trial waveforms • S5 anticipated sensitivity, determined using injected generic waveforms to determine minimum detectable in-band energy in GWs • Current sensitivity:EGW > 1 Msun @ 75 Mpc, EGW > 0.05 Msun @ 15 Mpc (Virgo cluster)

14. correlated signal in two IFOs  large crosscorr Outline of GRB-GWB search (from Leonor et al, (ExtTrig group), APS April 06) • search for short-duration gravitational-wave bursts (GWBs) coincident with gamma-ray bursts (GRBs)(39 events during the S2to S4 runs) see :“A search for gravitational waves associated with the gamma ray burst GRB030329 using the LIGO detectors", B. Abbott et al. [LIGO Scientific Collaboration], Phys. Rev. D 72, 042002 (2005) • use GRB triggers observed by satellite experiments distributed by the GCN and IPN Networks • Swift, HETE-2, INTEGRAL, IPN, Konus-Wind • include both “short” and “long” GRBs, SGRs etc • search the astrophysically motivated time interval of LIGO data (~180s) surrounding each GRB trigger (on-source segment) • waveforms of GWB signals associated with GRBs are not known so use crosscorrelation of two interferometers (IFOs) to search for associated GW signal • use crosscorrelation lengths of 25 ms and 100 ms to target short-duration GW bursts of durations ~1 ms to ~100 ms • use bandwidth of 40 Hz to 2000 Hz no evidence for GW bursts associated with GRBs using this sample

15. The GRB sample for LIGO S5 run (from Leonor et al, APS April 06) 53 GRB triggers in 5 months of LIGO S5 run (as of April 10, 2006) • most from Swift • 16 triple-IFO coincidence • 31 double-IFO coincidence • 6 short-duration GRBs • 11 GRBs with redshift • z = 6.6, farthest • z = 0.0331, (~120Mpc) nearest • performed GW burst search on this sample using same pipeline • No loud events seen that are inconsistent with expected probability distribution

16. SGR hyperflares are also of interest – Clark et al (Poster) • Soft g-ray Repeaters – quiescent X-ray sources with active periods of high luminosity soft g-ray bursts • though to be magnetars - extremely magnetic neutron stars • Occasionally emit hyperflares – 1000s of time as luminous as ordinary bursts and with a harder spectrum • Catastrophic global reconfiguration of the neutron star crust and magnetic field • Set up oscillations in the neutron star (e.g. possible torsional modes seen – Strohmayer and Watts, 2006) • Vibrational modes, like the fundamental mode, could be seen via gravitational waves as short duration ring-downs • Asteroseismology – study the equation of state of the star via modes, determine mass and radiius (Andersson and Kokkotas, 1998)

17. Characteristic search sensitivity hrss [strain/rHz] Search for QPOs after the SGR 1806-20 hyperflare (S. Marka) • The Soft Gamma-Ray Repeater SGR1806-20 emits a record flare ( d = [7.5 : 15 ] kpc, ~1046ergs ) • Magnetar model: energy release corresponds to the neutron star crust and magnetic field catastrophic re -arrangement • Quasi-periodic oscillations observed in lightcurve's tail of SGR1806-20 (Israel et al. (2005), Watts & Strohmayer (2006), Strohmayer & Watts (2006)) and SGR1900+14 (Strohmayer & Watts (2005)) • Excitation of neutron star's seismic modes is plausible • Subset of QPOs fall in LIGO's band

18. Gravitational wave sensitivity illustrated through energetics (S. Marka) • Assuming • isotropic emission • equal amount of power in both polarizations (circular polarization) • Egwiso is a characteristic energy radiated in the duration and frequency band we searched from a source at a distance of 10kpc • Egwiso = 2.6 x 10-8 Msun c2 (~4.6 x 1046 erg) for the best sensitivity of hrss= 3.5 x 10-22 strain/rHz (92.5Hz, BW=1.6Hz) • Repeat the analysis for recent flares (SGR1900+14 and SGR1806-20)

19. Plans for Advanced detectors : 2008- To move from detection to astronomy the current detector network will upgrade to a series of ‘Advanced’ instruments • Advanced LIGO will comprise a set of significant hardware upgrades to the US LIGO detectors • Advanced Virgo will be built on the same time scale as Advanced LIGO, and will achieve comparable sensitivity • Japan’s Large Cryogenic Gravitational Telescope (LCGT) will pioneer cryogenics and underground installation • GEO HF will improve the sensitivity beyond GEO600’s, mainly at high frequency

20. What is Advanced LIGO • Project to increase sensitivity (range) of LIGO by factor of ten • Uses existing sites, infrastructure • Implements higher power laser, new optics and monolithic suspensions, improved seismic isolation and other improvements • Increases number of GW emitting sources in range by factor of 1000 • Will enable study of significant number of astrophysical sources of gravity waves • Advanced LIGO will pioneer the new field of GW astronomy and astrophysics

21. Range of Advanced LIGO for 1.4 Mo binary neutron star inspirals . .

22. Advanced LIGO Astronomy & astrophysics with Advanced LIGO • Neutron Star Binaries: Initial LIGO: ~10-20 Mpc  Advanced LIGO: ~200-350 Mpc Most likely rate: 1 every 2 days • Black hole Binaries: Up to 10 Mo, at ~ 100 Mpc • up to 50 Mo, in most of the observable Universe • Stochastic Background: • Initial LIGO: ~3e-6 • Adv LIGO ~3e-9 • x10 better amplitude sensitivity • x1000 rate=(reach)3 •  1 year of Initial LIGO < 1 day of Advanced LIGO

23. Status of Advanced LIGO • Fully peer reviewed • Approved by National Science Board • Expect start of US construction funds in 2008 • UK (PPARC), Germany (MPG) contributions already funded • 6 year construction schedule; ~$200M cost • Funded from NSF account for big projects (MREFC) with operations to be supported by NSF Gravity Program (not from NSF Astronomy Program) • Initial operations expected in 2014

24. Advanced detector network h (Hz -1/2) F Frequency (Hz)

25. Gravitational Wave Astronomy GW detector systems now reaching levels where they may see signals associated with gamma ray bursts within the next few years. The essentially guaranteed detection of compact binary systems by the advanced detectors early in the next decade is likely lead to further understanding of the nature of the gamma ray bursts. A new way to observe the Universe