LISA

Search for gravitational wavesJo van den Brand

LISA

Introduction

Einstein gravity :

Gravity as a geometrySpace and time are physical objects

8G T

Gravitational waves

• Dynamical part of gravitation, all space is filled

• Very large energy, almost no interaction

• Ideal information carrier, almost no scattering or attenuation

• The entire universe has been transparent for GWs, all the way back to the Big Bang

LISA

Gravitational waves `squeeze’ space: small effects

Proper distance between x and x +dx

Plane GW propagating in z-direction

Define

Wave equation

LISA

Gravitational waves

L

Lh

2

GW

time

L-L L+L Predicted by general relativity

GW = space-time metric wave

– Distance variation

– Strain amplitude h:

GW produced by mass acceleration

– d = source distance

– Q = quadrupole moment ddt

Qd

c

Gh

122

2

4

Small coupling factor → astrophysical sources

1124410 mkgs

sJLG /10 16L=20 m, d = 2 m, 27 rad/s

JEHzm absorbed54225 1010

Earth-sun: 313 W

LISA

Evidence for gravitational waves

PSR 1913+16– R. Hulse, J. Taylor (1974)

– Binary pulsar (T = 7.75 hr)

– 1 pulsar (17 rev/s) → get the orbital parameters

– Orbital period decreases

– Energy loss due to GW emission (~3 x 1024 W)

– Good agreement with GR

– Inspiral lifetime about 300 Myears (3.5 m/yr)

– Expected strain, h~10-26 m

LISA

GW source: coalescing binary

End of the life of compact binary systems– Neutron stars, systems have been observed

Rare events– ~ 0.1 event/year (@20Mpc) ±1 order of magnitude

Typical amplitude (NS-NS): h ~ 10-22 @ 20 Mpc “Known” waveform

– Search with matched filtering

– General relativity tests

– Standard candles: get the distance from the waveform

– Coincidence with short gamma ray burst?

LISA

Two body problem in general relativity

Collision of two black holes

Numerical solution of Einstein equations required

Problem solution started 40 years ago (1963 Hahn & Lindquist, IBM 7090)

Wave forms critical for gravitational wave detectors

A PetaFLOPS-class grand challenge

LISA

Numerical relativity

First merger of three black holes simulated on a supercomputer

ScienceDaily (Apr. 12, 2008)

Manuela Campanelli, Carlos Lousto and Yosef Zlochower—Rochester Institute of Technology Center for Computational Relativity and Gravitation

Triple quasar (10.8 Gly)S. G. Djorgovski et al., Caltech, EPFL (Jan. 2007)

lymmmLmL 110)10/()10(1 16226

kmmmmLmL 1010)10/()10(10 4221818

LISA

Interferometric detectors: an international dream

GEO600 (British-German)Hanover, Germany

LIGO (USA)Hanford, WA and Livingston, LA

TAMA300 (Japan)Mitaka

VIRGO (French-Italian)Cascina, Italy

AIGO (Australia), Wallingup Plain, 85km north of Perth

LISA

Virgo: science case

First (?) direct observation of gravity waves

Better understanding of gravity – GW produced in high density area

– Strong field

– Tests GR

Open a new window on the universe– GW very weakly absorbed

– Standard candle: Hubble constant

– GW + Gamma Ray Bursts?

– Supernova understanding?

– Neutron stars/black hole physics?

– Early universe picture??

Pushing interferometer techniques to their limits

LISA

Interferometer as GW detector

Principle: Measure distances between free test masses

– Michelson interferometer

– Test masses = Interferometer mirrors

– Sensitivity: h = L/L

– We need large interferometer

– For Virgo L = 3 km

2

hLL 2

hLL

Suspended mirror

Suspended mirror

Beam splitter

LASER

LightDetection

Virgo: CNRS+INFN(ESPCI-Paris, INFN-Firenze/Urbino, INFN-Napoli, INFN-Perugia, INFN-Pisa, INFN-

Roma,LAL-Orsay, LAPP-Annecy, LMA-Lyon, OCA-Nice)

+ NIKHEF joined 2007

First science run: May – September 2007

LISA

Interferometer Concept

As a wave passes, the arm lengths change in different ways….

…causing the interference pattern

to change at the photodiode

SuspendedMasses

LISA

Laser 20 W

Input Mode Cleaner (144 m)

Power

Recycling

3 km long Fabry-Perot

Cavities

Output Mode

Cleaner (4 cm)

Input mode cleaner

Mode cleaner cavity: filters laser noise, select TEM00 mode

LISA

Installation in IMC end tower

Each switch has been tested in open and closed position.The mirror and RM are moved55 mm for- and backwards.

LISA

Eric Hennes

Nikhef: redesign and replace dihedron

Optronica

Marinebedrijf Den Helder

Zorg dat je erbij komt…

LISA

Nikhef: Linear alignment of VIRGO

N

W

EOM

Phase modulation of input beam

Demodulation of photodiode signals at different output beams

– => longitudinal error signals

Quadrant diodes in output beams

– => Alignment information

– (differential wavefront sensing)

Anderson-Giordano technique

– 2 quadrant diodes after arm cavities

+ Han Voet

LISA

Linear alignment setup

LISA

Rotating asymmetric neutron star

GW Amplitude function of the unknown asymmetry

– ε = star asymmetry = ??

– Upper limit set by the pulsar spin down

A few pulsars around a few 100 Hz

– Only 800 pulsars plotted out of 109 in the galaxy

Weak signal but could be integrated for months

– But a complex problem due to the Doppler effect

– CPU issues

GW source: pulsars

6

2

24527

1020010

10103

Hz

f

cmg

I

r

kpch zz

f (Hz)

N

LIGO: <10% of energy in GW

Crab pulsar

LISA

Periodic Sources – all sky search – Roma / NIKHEF

• Doppler shifts• Frequency modulation: due to Earth’s motion

• Amplitude modulation: due to the detector’s antenna pattern.

• Assume original frequency is 100 Hz and the maximum variation fraction is of the order of 0.0001

• Note the daily variations

• After FFT: energy not in a single bin, so the SNR is highly reduced

• Bin in galactic coordinates

• Re-sampling

• Short FFTs

• Hough maps

• Include binary systems

ALL SKY SEARCH enormous computing challenge

(Sipho van der Putten, Henk Jan Bulten, Sander Klous)

LISA

GWs from binaries

Frequency changes a lot due to Doppler: df/f~10-3

Hulse-Taylor:

_Towards DetectorV

Grid-based analysisExtension of LIGO – Virgo CW analysisCalibration systems for LISA

LISA

Virgo sensitivity compared to LIGO and GEO600

May 2 Inspiral range 6.5 Mpc

The horizon (best orientation) for a binary system of two 10 solar mass black holes is 63 Mpc

LISA

Discovery potential first event

Hypothesis:

– Finesse = 150 (now : 50)

– Same losses & power recycling as today

Horizon (Virgo+)

– BNS: 150 Mpc (optimal orientation)

– BBH: 750 Mpc (optimal orientation)

BNS Rates: (most likely and 95% interval)

– Initial Virgo (30Mpc) 1/100yr (1/500 -1/25 yr)

– Enhanced LIGO (60Mpc) 1/10yr (1/50- 1/2.5yr)

– Virgo+ limit (150Mpc) 1.2/yr (1/4yr-5/yr)

– Advanced detectors (350Mpc) 40/yr (8-160/yr)

Kalogera et al; astro-ph/0312101; Model 6

BBH and other sources rates are more difficult to predict

LISA

LIGO and VIRGO: scientific evolution

At present hundreds of galaxies in range for 1.4 Mo NS-NS binaries

Enhanced program– In 2009 about 10 times

more galaxies in range

Advanced detectors– About 1000 times more

galaxies in range

– In 2014 expect 1 signal per day or week

– Start of gravitational astrophysics

– Numerical relativity will provide templates for interpreting signals

LISA

Advanced Virgo: vacuum – cryo links

6885985

Gas load from mirror 10-4 mbar l/s

mbar

Element number

Start pressure

Intermediate

Final pressure

Pressure

LISA

LN2 GN2

Beam vacuum

Isolation vacuum

LN2

Fixed 300 K

3.2 mm/m

3.2 mm/m

Reinforce rib

Forces

Vacuum + super isolation

Tie rod

Advanced Virgo: vacuum – cryo links

LISA

Advanced Virgo: superattenuator

FEA:

Frans MulCorijn

LISA

Other activities in GW program

Einstein Telescope – conceptual design study

– Approved in May 2008

– Funded for 3 years

– Nikhef responsible for Working Group 1 on site selection

Design Study Proposal approved by EU within FP7

Large part of the European GW community involved EGO, INFN, MPI, CNRS, NIKHEF, Univ. Birmingham, Cardiff, Glasgow

Recommended in Aspera / Appec roadmap

LISA

28

GRB050509B

3RD GENERATIONINTERFEROMETER

2ND

GENERATION

1ST GENERATION

Credit G.Cagnoli

NS - NS INSPIRAL RANGE

Virgo

LOI to ESA – LISA analysisNikhef, VU, RUN and SRONNetherlands: Bulten/Nelemans

Beyond Einstein is the umbrella program for a series of NASA/ESA missions linked by powerful new technologies and common science goals to answer the questions:

Gravitational Waves Can Escape from Earliest Moments of the Big

Bang

Inflation(Big Bang plus 10-34 Seconds)

Big Bang plus 300,000 Years

gravitational waves

Big Bang plus 14 Billion Years

light

Now

What powered the Big Bang?

Is Einstein’s theory still right in these conditions of extreme gravity? Or is new

physics awaiting us?

Chandra - Each point of x-raylight is a Black Hole!

What happens at the edge of a Black Hole?

Dark energy and matter interact through gravity

We do not know what 95% of the universe

is made of!

What is the mysterious Dark Energy pulling the Universe apart?

September 6, 2007: Committee on NASA's Einstein Program: An Architecture for Implementation, National Research Council

Finding 4. LISA is an extraordinarily original and technically bold mission concept. LISA will open up an entirely new way of observing the universe, with immense potential to enlarge our understanding of physics and astronomy in unforeseen ways. LISA, in the committee’s view, should be the flagship mission of a long-term program addressing Beyond Einstein goals.

Finding 8. The present NASA Beyond Einstein funding wedge alone is inadequate to develop any candidate Beyond Einstein mission on its nominal schedule. However, both JDEM and LISA could be carried out with the currently forecasted NASA contribution if DOE's contribution that benefits JDEM is taken into account and if LISA's development schedule is extended and funding from ESA is assumed.

LISA

Summary

Gravitational wave physics– Component of our Astroparticle Physics initiative

– Exciting new physics program

– Important questions are addressed

– Program with a long-term scientific perspective

VIRGO– Sensitivity is improving fast

– First science run underway

– Data sharing and analysis between LIGO and Virgo

NIKHEF commitment – Modest at this moment

– Expand to FOM research program in 2009 / 2010