Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session T7: Gravitational Wave Astrophysics with LISA |
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Sponsoring Units: GGR DAP Chair: Joan Centrella, NASA-GSFC Room: Hyatt Regency Jacksonville Riverfront Grand 8 |
Monday, April 16, 2007 1:30PM - 2:06PM |
T7.00001: Gravitational Wave Backgrounds and Bursts from Terascale Phase Transitions and Cosmic Strings Invited Speaker: The millihertz frequency band probed by LISA corresponds to horizon scales at the Terascale frontier in the relativistic early Universe. A first order phase transition, possibly associated with electroweak or supersymmetry breaking, late inflationary reheating, or activity and stabilization of warped extra dimensions of space, causes supercooling, cavitation, catastrophic explosive bubble growth, and relativistic turbulence, leading to bulk motions of matter on what was then a submillimeter scale, and efficient gravitational wave production. LISA is capable of detecting a stochastic background from such events at cosmic temperatures from about 100 GeV to about 1000TeV, if gravitational waves in the LISA band were produced with an overall efficiency more than about $10^{-7}$, a typical estimate from a moderately strong relativistic first-order phase transition, and about a million times below current limits from big bang nucleosynthesis. This corresponds to times about $10^{-10}$ to $10^{-18}$ seconds after the start of the Big Bang, a period and range of scales not directly accessible with any other technique. LISA also deeply probes possible new forms of energy such as cosmic superstrings, relics of the early Universe predicted to form by certain kinds of symmetry breaking at the end of inflation, that are invisible in all ways except by the gravitational waves they emit. Estimates are presented of predicted spectra of gravitational wave backgrounds from cosmic strings, current limits on their mass per length from millisecond pulsar timing limits on gravitational waves, and the new discovery space probed by LISA. In addition, cusp catastrophes in the oscillations of nearby cosmic strings sometimes beam gravitational waves in our direction leading to a burst with a cleanly predicted waveform signature; estimates will be presented of the predicted rate and detectability of these events. [Preview Abstract] |
Monday, April 16, 2007 2:06PM - 2:42PM |
T7.00002: Gravitational waves as probes of galactic nuclei and accretion physics Invited Speaker: The NASA/ESA Laser Interferometer Space Antenna (LISA) mission is expected to measure, with exquisite precision, the low frequency gravitational waves from tens of super-massive ($10^4-10^7M_\odot$) merging black holes in galactic nuclei at redshifts up to 30, and hundreds of compact objects captured by supermassive black holes in galactic nuclei at redshifts $<2$. The long gravitational waveforms will enable precise measurements of the masses, spins, and orbital parameters of these systems, as well as distances and approximate positions. Many of these events are likely to have electromagnetic counterparts: precursors, prompt variability and afterglows from circumbinary disks around the black hole binaries, and tidal disruptions or disk perturbations due to the captured compact objects. The electromagnetic and gravitational wave measurements of these events will provide unprecedented probes of accretion disk structure, and the structure and dynamical interactions between stars, black holes and gas in the central light-year of galaxies. [Preview Abstract] |
Monday, April 16, 2007 2:42PM - 3:18PM |
T7.00003: Coevolution of galaxies and massive black holes Invited Speaker: Massive black holes, with masses in the range of a few thousand to a few million solar masses, which merge with a companion black hole of similar mass are expected to be the most powerful sources of gravitational radiation in the LISA band. Such black hole binaries can be detected by LISA basically at any redshift of interest. Gravitational waves from black hole mergers can serve as a powerful tool to study the early evolution of the whole black hole population. I review scenarios for the co-evolution of massive black holes and cosmological structures, where the first black holes form in pre-galactic structures. These black holes evolve then in a hierarchical fashion, following the merger hierarchy of their hosts. Accretion of gas, traced by quasar activity, plays a fundamental role in determining the two parameters defining a black hole, mass and spin. Gravitational waves, together with observations in electromagnetic bands, can help constrain the evolution of both MBH mass and spin. [Preview Abstract] |
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