Science Promise of LISA

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Science Promise of LISA

• Bernard Schutz
• Albert Einstein Institute
• Potsdam/Golm Germany
• http//www.aei.mpg

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Space-based GW Detection

• LISA Pathfinder, a technology demonstrator for
  LISA, will be launched by ESA in 2007.
• Planning managed by 20-member LISA International
  Science Team (LIST)
• Various working groups see http//www.srl.caltech
  .edu/lisa

• LISA will consist of 3 spacecraft flying
  independently in a triangular formation.
• Launch expected 2012
• LISA is a joint project of ESA and NASA, 50-50
  sharing of responsibility and science.

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Dynamics Graphically
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LISA extends LIGO to low frequency
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Gravitational Waves
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RICH Scientific Harvest

• High Signal-to-Noise observations of
• Coalescences of supermassive black hole binaries
• White-dwarf binary systems in our Galaxy
• Precision tests of general relativity by
  observing details of orbits of small black holes
  captured by large ones
• Limits on (or even detection of) a background of
  gravitational waves from the Big Bang
• Strong potential for new discoveries
  intermediate-mass black holes, cosmic string
  kinks and cusps, compact dark-matter objects,

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The LISA Constellation

• 20 degrees behind Earth in its orbit
• Advanced technology
• Drag-free control to minimize disturbances
• Laser transponding to maintain light power
• Interferometry at pico-meter scale, much less
  demanding than on ground.

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LISA as an Observatory

• LISA has a complex antenna pattern two
  independent Michelson interferometers, can be
  operated as a phased array .
• As it rotates, amplitude modulation provides
  directional information.
• As it moves, Doppler modulation provides
  additional directional information, above 1 mHz.
• Data transmitted to ground as a number of
  time-series. Data analysis is more complex than
  ground-based.

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Modulation-aperture Synthesis
Wave ( f 16 mHz)

• Using phase modulation is equivalent to aperture
  synthesis. Gives diffraction limit ?? ?/ 1
  AU.
• Black hole coalescences will benefit from
  templates based on good numerical simulations in
  next decade.
• Measurements on detected sources - ?? 1
  1o - ?(mass,distance) ? 1

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Supermassive Black Holes

• Ubiquitous almost all galaxies have them.
• Major theme of this meeting.
• Challenges
• Observations extend mass range, identify host
  galaxies
• Theory compute merger timescales, compute merger
  waveforms

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SMBH Merger Science

• SMBHs seem to have accompanied galaxy formation.
• Merger history enlightens galaxy history
• Mergers are standard candles, can potentially
  measure acceleration history of the Universe

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Compact White-Dwarf Binaries

• LISA will see thousands of binaries, all the
  binaries in the Galaxy in its frequency window,
  many already known LISA calibration sources.
• So many that at low frequencies there will be
  source confusion.
• LISA will provide crucial information concerning
  populations, orbits, binary and stellar evolution.

• Challenges coordinated observations, dealing
  with source confusion.

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Capture 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.

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Capture orbits (2)

• Challenges
• Computing the orbits, a major theme of this
  meeting
• Filtering the data to find these orbits in a huge
  parameter space
• Dealing with source confusion the Olbers limit

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Extraction of LISA Signals

• Subtle interferometry done by beating light from
  different lasers
• Laser noise must be removed
• 12 signals available, three Michelson
  combinations extracted by time-delay
  interferometry (TDI)
• 4th Sagnac combination cancels GW signal at
  low-f

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Data Analysis Challenges

• Huge parameter space for capture orbits
• Strong interaction between searches for different
  sources
• SMBH signals distort noise, must be removed well
• Binary confusion noise edge must be removed,
  improves with time
• Capture orbit confusion may have to be done
  simultaneously
• Careful planning, plus prior research and
  simulation essential!
• Coordination with astronomical community equally
  important.

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Beyond LISA

• LISA is the first GW detector in space, but
  already we know we want to learn more
• Observe Big Bang down to the inflation limit
• Observe differential redshift in NS-NS binary
  signals from expansion of universe during
  emission.
• Currently developing BBO Big Bang Observer, as
  an illustration to NASA of what the next mission
  could look like. Observe in Gap region where
  backgrounds are low.