esat/science/lisa

1. 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

2. 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

3. 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

4. Bar detectors: IGEC collaboration • Built to detect gravitational waves from compact objects

5. SFERA Mini-GRAIL: a spherical `bar’ in Leiden

6. 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

7. Network of Interferometers LIGO Virgo GEO TAMA AIGO decompose the polarization of gravitational waves detection confidence locate the sources

8. Virgo

9. As a wave passes, the arm lengths change in different ways…. Interferometer Concept …causing the interference pattern to change at the photodiode Suspended Masses

10. VIRGO Optical Scheme Input Mode Cleaner (144 m) 3 km long Fabry-Perot Cavities Laser 20 W Power Recycling Output Mode Cleaner (4 cm)

11. Virgo – inside the central building

12. 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

13. Superattenuators Possible contributions: • Virgo+ will use monolythic suspension • Input-mode cleaner suspension

14. Input beam Transm. beam Refl. beam Input mode cleaner • Mode cleaner cavity: filterslaser noise, select TEM00 mode

15. 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.

16. Sensitivity evolution LIGO started commissioning first arm in 1999

17. Virgo compared to LIGO

18. 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

19. 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

20. 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

21. 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.

22. 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.

23. 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?...

24. 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+

25. 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

26. 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)

27. 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

28. LISA science: massive black hole mergers MBH = 0.005Mbulge But do they merge? D. Richstone et al., Nature 395, A14, 1998

29. 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]

30. Typical EMRI event: 10 MBH 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.

31. 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

32. 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)

33. 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

34. 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

35. 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