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LISA. Laser Interferometer Space Antenna. Status of Gravitational Physics Program Jo van den Brand NIKHEF – Annual Scientific Meeting 2005. http:// www.esa.int/science/lisa. October 3, 2005. Einstein gravity : Gravity as a geometry Space and time are physical objects. Introduction.
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LISA Laser Interferometer Space Antenna Status of Gravitational Physics Program Jo van den Brand NIKHEF – Annual Scientific Meeting 2005 http://www.esa.int/science/lisa October 3, 2005
Einstein gravity : Gravity as a geometry Space and time are physical objects Introduction • 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 transparant for GWs, all the way back to the Big Bang
Proper distance between xm and xm +dxm Define Wave equation Plane GW propagating in z-direction Amplitude, frequency and duration Gravitational waves `squeeze space: small effects
Bar detectors: IGEC collaboration • Built to detect gravitational waves from compact objects
SFERA Mini-GRAIL: a spherical `bar’ in Leiden
VIRGO (French-Italian) Cascina, Italy AIGO (Australia), Wallingup Plain, 85km north of Perth Interferometric detectors: an international dream GEO600 (British-German) Hanover, Germany LIGO (USA) Hanford, WA and Livingston, LA TAMA300 (Japan)Mitaka
Network of Interferometers LIGO Virgo GEO TAMA AIGO decompose the polarization of gravitational waves detection confidence locate the sources
As a wave passes, the arm lengths change in different ways…. Interferometer Concept …causing the interference pattern to change at the photodiode Suspended Masses
VIRGO Optical Scheme Input Mode Cleaner (144 m) 3 km long Fabry-Perot Cavities Laser 20 W Power Recycling Output Mode Cleaner (4 cm)
Mirror suspension • High quality fused silica mirrors • 35 cm diameter, 10 cm thickness, 21 kg mass • Substrate losses ~1 ppm • Coating losses <5 ppm • Surface deformation ~l/100
Superattenuators Possible contributions: • Virgo+ will use monolythic suspension • Input-mode cleaner suspension
Input beam Transm. beam Refl. beam Input mode cleaner • Mode cleaner cavity: filterslaser noise, select TEM00 mode
Interferometer alignment and control • Quadrant photodiodes provide the error signals to control the angular positions of the mirrors • High precision ADCs, demod, filtering, etc. Discussion on Jan. 25th.
Sensitivity evolution LIGO started commissioning first arm in 1999
Virgo-LIGO joint analysis • Working group for burst and inspiral events • Up to now work on simulated data : • Project “1a”: Compare analysis pipelines on the same data sets. • Project “2b”: Study the advantages of 3 sites for astrophysical sources • Sky location, Detection efficiency • 3 talks and papers (GWDAW9 and Amaldi 6) Burst from galactic center
Virgo- Bars joint analysis • AURIGA, ROG • Burst events and Stochastic signals • Project starting with software injection • 4 hours of data • Plan for analysis C6 &C7
28 Radio Sources Detection of Periodic Sources • Pulsars in our galaxy: “periodic” • search for observed neutron stars • all sky search (computing challenge) h ~ GIf2ee/cr < 10-24
Periodic Sources – all sky search • Doppler shifts • Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes • Amplitude modulation due to the detector’s antenna pattern. • Theoriginal frequency is 100 Hz and the maximum variation fraction is of the order of 0.0001 • Note the daily variations. • Because of the frequency variation, the energy of the wave doesn’t go in a single bin, so the SNR is highly reduced.
Optimal detection by re-sampling procedure • Use a non-uniform sampling of the received data: if the sampling frequency is proportional to the (varying) received frequency, the samples, seen as uniform, represent a constant frequency sinusoid and the energy goes only in one bin of their FFT. • Every point of the sky (and every spin-down or spin-up behavior) needs a particular re-sampling and FFT. Original data: The frequency is varying, we sample non-uniformly (about 13 samples per period). ALL SKY SEARCH enormous computing challenge The non-uniform samples, seen as uniform, give a perfect sinusoid and the periodogram of the samples has a single “excited” bin.
VIRGO - Next steps • Sept-Dec 05: “Injection” shutdown • 2-3 months of work • New injection bench; Power should go up by a factor 10 • New recycled mirror: Better controls • Miscellaneous changes • Followed by the new injection system commissioning • 2006: Commissioning + data taking • Alignment, controls,… • A science run by the end of 2006 (coincidence with LIGO-S5) ? • 2007 • Data taking/Commissioning/Upgrades • 2008-9: Virgo + • 50W laser, New electronics, New mirrors ? (not yet decided) • 2011(?): Advanced Virgo • 200W laser? New beam geometry? New mirrors?...
Gravitational wave antenna in space - LISA • 3 spacecraft in Earth-trailing solar orbit separated by 5 x106 km. • Measure changes in distance between fiducial masses in each spacecraft • Partnership between NASA and ESA • Launch date ~2013+
LISA Interferometry • “LISA is essentially a Michelson Interferometer in Space” • However • No beam splitter • No end mirrors • Arm lengths are not equal • Arm lengths change continuously • Light travel time ~17 seconds • Constellation is rotating and translating in space
Rotating Neutron Stars Complementarity of Space- & Ground-Based Detectors Difference of 104 in wavelength: Like difference between X-rays and IR! VIRGO LISA LISA will see all the compact white-dwarf and neutron-star binaries in the Galaxy (Schutz)
LISA – Technical contributions NL SRON • Test equipment for position sensor read-out electronics in on-ground tests of the satellite system • Simulation software modules of the position sensors, used in system simulations TNO-TPD • Test equipment of the Laser Optical Bench • Decaging Mechanism (TBC) Bradford Engineering • Cold Gas propulsion (TBC) NIKHEF • ASIC development for read-out electronics
LISA science: massive black hole mergers MBH = 0.005Mbulge But do they merge? D. Richstone et al., Nature 395, A14, 1998
Massive black hole mergers • Several observed phenomena may be attributed to MBH binaries or mergers • X-shaped radio galaxies (see figure) • Periodicities in blazar light curves (e.g. OJ 287) • X-ray binary MBH: NGC 6240 • See review by Komossa [astro-ph/0306439] [Merritt and Ekers, 2002]
Typical EMRI event: 10 MBH captured by 106 M BH EMRI - capture orbits • Filtering the data to find these orbits in a huge parameter space • Dealing with source confusion • Challenges: • Computing the orbits • Stellar-type black holes (10 M) sometimes fall into supermassive holes. • Orbits complicated, can have 104 or more cycles, provide detailed examination of black-hole geometry. • Tests of black-hole no-hair theorems, strong-field gravity.
Production: fundamental physics in the early universe- Inflation, phase transitions, topological defects- String-inspired cosmology, brane-world scenarios • Spectrum: slope, peaks give masses of key particles & energies of transitions. • A TeV phase transition would have left radiation in LISA band. Primordial gravitational waves
Logistics • SRON • Netherlands Institute for Space Research • Radboud Universiteit Nijmegen • Department of astrophysics • NIKHEF • National institute for nuclear and particle physics • Vrije Universiteit - Amsterdam • Subatomic physics group Interest expressed by astronomy groups of both Leiden & Utrecht Universities Henk Jan Bulten & Gijs Nelemans (RUN) – DAST representatives NL for LISA (ESA)
Summary • Collaborate on LISA and VIRGO • Component of our particle-astrophysics initiative • Exciting new physics program at NIKHEF • NIKHEF commitment • NIKHEF • Thomas Bauer, Harry van der Graaf, Jan Willem van Holten, Frank Linde • Sipho van der Putte – OIO • VU • Jo van den Brand, Henk Jan Bulten, Tjeerd Ketel • Gideon Koekoek - AIO • Technical impact to be determined • Mechanical engineering, ASIC design, GRID • Negotiate with SRON, LISA and VIRGO • Define responsibilities
Optical bench TM1 Sensor housings TM2 LISA Pathfinder • Goal: demonstrate free-fall of a proofmass, i.e. isolation from non-gravitational disturbances. • Method: laser interferometry between two proof masses (PMs) Dimensions: 640 mm x 375 mm x 375 mm
LISA Science Goals & Sources Science Objectives: • Determine the role of massive black holes in galaxy evolution, including the origin of seed black holes • Make precision tests of Einstein’s Theory of Relativity • Determine the population of ultra-compact binaries in the Galaxy • Probe the physics of the early universe Observational Targets: • Merging supermassive black holes • Merging intermediate-mass/seed black holes • Gravitational captures by supermassive black holes • Galactic and verification binaries • Cosmological backgrounds