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Gravitational Waves from Black Hole Mergers Joan Centrella NASA/GSFC Science Writer’s Workshop 2007 Spring Symposium on Black Holes Space Telescope Science Institute April 25, 2007. ripples in curvature of spacetime, v = c
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Gravitational Waves from Black Hole Mergers Joan Centrella NASA/GSFC Science Writer’s Workshop 2007 Spring Symposium on Black Holes Space Telescope Science Institute April 25, 2007
ripples in curvature of spacetime, v = c predicted by Einstein’s General Relativity Binary black hole mergers are very strong sources of gravitational waves Luminosity ~ 1023 Lsun > luminosity of all the stars in observable universe combined! Massive black hole binary mergers are observable by LISA to high redshift Stellar black hole binary mergers are sources ground-based detectors like LIGO Gravitational waves…. cosmic messengers
final merger occurs in strong-field gravity need to solve Einstein’s equations on computer Very difficult problem! efforts for over 30 years instabilities, codes crashed… Recent breakthroughs: 2004: first complete orbit 2005: first complete merger + GWs 2005: new methods accelerate progress Era of rapid progress, new results, many groups… The fingerprints of BH mergers…
Comparison of results… • Equal mass, nonspinning case • 3 different , independently-written codes
Longer waveforms… • Equal mass, nonspinning case • ~ 7 orbits before merger • Match numerical waveform to PN • apply to gravitational wave data analysis • improve templates for LIGO • prepare for LISA data analysis…
Recoil kicks from BBH mergers... • When m1≠m2, or when BHs are spinning, GW emission is asymmetric • GWs carry momentum, so merged remnant BH suffers recoil ‘kick’ • If kick is large enough, the remnant BH that forms may be ejected from its host structure • Nonspinning BHs: • max kick velocity ~ 175 km/s • Spins perpendicular to orbital plane: • kicks up to ~ 400 km/s • Spins in the orbital plane: • can produce very large kicks…up to 2000 km/s, possibly larger!
Spinning Black Holes: The Movies • m1 = m2 • each BH has a/m ~ 0.9 • Final BH has: • a/m ~ 0.67 • vkick ~ 1500 km/s in +z direction (Visualizations by Chris Henze, NASA/Ames)
Spinning Black Holes: The GWs (Visualizations by Chris Henze, NASA/Ames)