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Gravitational Astrophysics Lab staff are involved in many research areas, including:
Binary black hole (BBH) mergers are among the strongest and most spectacular sources of
gravitational waves for LISA and ground-based detectors such as LIGO. We develop 3-dimenensional numerical
simulations of Einstein's gravitational field equations to model strong field binary
black hole merger interactions and to calculate the resulting gravitational waveforms.
The Laser Interferometer Space Antenna (LISA) mission will detect
gravitational waves in the frequency band between 10-4 and 1 Hz. This
band is expected to contain signals from diverse astrophysical sources
throughout the Universe, such as merging supermassive black holes,
hierarchical mergers of intermediate mass black holes leading up to
supermassive black holes, compact stellar objects spiraling into
supermassive black holes in galactic nuclei, thousands of close binaries
of compact objects in the Milky Way and possibly backgrounds of
cosmological origin. This unprecedented view of the Universe will reveal
fundamental phenomena not easily observed by any other means.
EUD scientists are modeling the nonlinear merger phase of massive
black hole coalescence using large scale computer codes that solve the
Einstein equations of general relativity. These codes calculate the
gravitational wave signatures of black hole mergers that are essential for
LISA source identification and data analysis. Since the gravitational
waveforms and binary dynamics scale with the masses and spins of the black
holes, these results apply to supermassive black hole coalescences from
galaxy mergers as well as intermediate mass "seed" black holes from
hierarchical structure formation. They also apply to stellar black hole
coalescences that are important for the ground-based detectors such as
LIGO, VIRGO, and GEO.
GSFC has been designated as the lead center for NASA's role in the LISA
mission. LISA is a joint ESA-NASA project to construct the first
space-based gravitational wave detector. Goddard scientists and engineers
are engaged in the formulation of the mission with their co-workers at the
Jet Propulsion Laboratory and ESA and the broader research community in
the U.S. and Europe. At GSFC, LISA personnel are working on engineering
studies, integrated modeling and technology development. The GSFC work on
technology development, which is largely centered at LHEA, focusses on
materials stability, optical metrology, laser stabilization and
micronewton thruster testing. GSFC also hosts the
AstroGravS archive of gravitational wave sources, containing literature links and
a catalog of waveforms.
At the right are recent results from calcuations of the
optical depth of the universe to high energy gamma-rays as a function of
both redshift and gamma-ray energy. These results will be used in
interpreting GLAST data and to test special relativity at high energies
and to test some quantum gravity models and extra dimension models. Credit: Floyd Stecker,
click to enlarge image.
EUD scientists are modeling high-energy astrophysics sources that produce cosmic rays,
gamma rays, and x-rays. Much of the recent effort has been on gamma ray bursts, active
galactic nuclei, pulsars and jets, with results relevant to a variety of high-energy
missions, including Swift, HETE, GLAST, XMM, and Chandra. View a PowerPoint slide about this topic.
Laboratory work at the Gravitational Astrophysics Lab centers on the development of
precision laser interferometry in support of the LISA mission, as well as other EUD missions
including TPF-C and MAXIM. The technology involves: laser stabilization, where
the frequency variations of a laser are attenuated by comparing it to an ultra-quiet
frequency reference; laser metrology, where methods are being developed to measure
and control variations in detectors and telescopes smaller than the size of an atom; and
space qualification issues related to the laser stabilization and metrology
technologies.
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