Gravitational Wave – GRB connections?

Jim HoughInstitute for Gravitational Research

University of Glasgow

Royal Society September 2006

‘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 L

Lh

~

Sources – the gravitational wave spectrum

Gravity gradient wall

ADVANCED GROUND - BASED DETECTORS

“Indirect”detection

of gravitational waves

PSR 1913+16

Evidence for gravitational waves

One cycle

Fabry-Perot/MichelsonInterferometer

Gravitational waves have very weak effect: Expect movements of less than a trillionth of the wavelength of light (10-18 m) over 4km

Detection of Gravitational waves

Consider the effect of a wave on a ring of particles :

GW detector network

GEO 600

600m

Gravitational wave network sensitivity

Frequency (Hz)

Gra

vit

ati

on

al w

ave a

mp

litu

de h

(/

Hz)

LIGO now at design sensitivity

Science data runs to date

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

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)

Gravitational Waves from compact binaries

Estimates give upper bound of 1/3 yr in LIGO S5

Binary Coalescence Sources & Science:

Image: R. Powell

LIGO Range

binary neutron star max. distance

binary black hole max.distance

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)

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

i ii

j kj k

crosscorrx y

x y2 2

correlated signal in two IFOs large crosscorr

no evidence for GW bursts associated with GRBs using this sample

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

SGR hyperflares are also of interest – Clark et al (Poster)

Soft -ray Repeaters – quiescent X-ray sources with active periods of high luminosity soft -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)

• 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

Search for QPOs after the SGR 1806-20 hyperflare (S. Marka)

dth(t)h2

rss

Characteristic search sensitivity

h rss

[str

ain

/rH

z]

Gravitational wave sensitivity illustrated through energetics (S. Marka)

• Assuming

» isotropic emission

» equal amount of power in both polarizations (circular polarization)

• Egw

iso is a characteristic energy radiated in the duration and frequency band we

searched from a source at a distance of 10kpc

» Egw

iso = 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)

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

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

Range of Advanced LIGO for 1.4 Mo binary neutron star inspirals

. .

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

Advance

d LIGO

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

Fused silicafibres or ribbons

Cantileverblades

Advanced detector network

Frequency (Hz)

h (Hz -1/2)

F

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