Engineering topics

Hughes, Scott A

Publications and source records attributed to Hughes, Scott A.

5 records

DOE OSTI2011

Systematics of black hole binary inspiral kicks and the slowness approximation

During the inspiral and merger of black holes, the interaction of gravitational wave multipoles carries linear momentum away, thereby providing an astrophysically important recoil, or 'kick' to the system and to the final black hole remnant. It has been found that linear momentum during the last stage (quasinormal ringing) of the collapse tends to provide an ''antikick'' that in some cases cancels almost all the kick from the earlier (quasicircular inspiral) emission. We show here that this cancellation is not due to peculiarities of gravitational waves, black holes, or interacting multipoles, but simply to the fact that the rotating flux of momentum changes its intensity slowly. We show furthermore that an understanding of the systematics of the emission allows good estimates of the net kick for numerical simulations started at fairly late times, and is useful for understanding qualitatively what kinds of systems provide large and small net kicks.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

Extreme mass-ratio inspirals in the effective-one-body approach: Quasicircular, equatorial orbits around a spinning black hole

We construct effective-one-body waveform models suitable for data analysis with the Laser Interferometer Space Antenna for extreme mass-ratio inspirals in quasicircular, equatorial orbits about a spinning supermassive black hole. The accuracy of our model is established through comparisons against frequency-domain, Teukolsky-based waveforms in the radiative approximation. The calibration of eight high-order post-Newtonian parameters in the energy flux suffices to obtain a phase and fractional amplitude agreement of better than 1 rad and 1%, respectively, over a period between 2 and 6 months depending on the system considered. This agreement translates into matches higher than 97% over a period between 4 and 9 months, depending on the system. Better agreements can be obtained if a larger number of calibration parameters are included. Higher-order mass-ratio terms in the effective-one-body Hamiltonian and radiation reaction introduce phase corrections of at most 30 rad in a 1 yr evolution. These corrections are usually 1 order of magnitude larger than those introduced by the spin of the small object in a 1 yr evolution. These results suggest that the effective-one-body approach for extreme mass-ratio inspirals is a good compromise between accuracy and computational price for Laser Interferometer Space Antenna data-analysis purposes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

EXPLORING SHORT GAMMA-RAY BURSTS AS GRAVITATIONAL-WAVE STANDARD SIRENS

Recent observations support the hypothesis that a large fraction of 'short-hard' gamma-ray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitational-wave (GW) measurements of well-localized inspiraling binaries can measure absolute source distances, simultaneous observation of a binary's GWs and SHB would allow us to directly and independently determine both the binary's luminosity distance and its redshift. Such a 'standard siren' (the GW analog of a standard candle) would provide an excellent probe of the nearby (z {approx}< 0.3) universe's expansion, independent of the cosmological distance ladder, thereby complementing other standard candles. Previous work explored this idea using a simplified formalism to study measurement by advanced GW detector networks, incorporating a high signal-to-noise ratio limit to describe the probability distribution for measured parameters. In this paper, we eliminate this simplification, constructing distributions with a Markov Chain Monte Carlo technique. We assume that each SHB observation gives source sky position and time of coalescence, and we take non-spinning binary neutron star and black hole-neutron star coalescences as plausible SHB progenitors. We examine how well parameters (particularly distance) can be measured from GW observations of SHBs by a range of ground-based detector networks. We find that earlier estimates overstate how well distances can be measured, even at fairly large signal-to-noise ratio. The fundamental limitation to determining distance proves to be a degeneracy between distance and source inclination. Overcoming this limitation requires that we either break this degeneracy, or measure enough sources to broadly sample the inclination distribution.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2010

Falloff of radiated energy in black hole spacetimes

The goal of much research in relativity is to understand gravitational waves generated by a strong-field dynamical spacetime. Quantities of particular interest for many calculations are the Weyl scalar {psi}{sub 4}, which is simply related to the flux of gravitational waves far from the source, and the flux of energy carried to distant observers, E. Conservation laws guarantee that, in asympotically flat spacetimes, {psi}{sub 4{proportional_to}}1/r and E{proportional_to}1/r{sup 2} as r{yields}{infinity}. Most calculations extract these quantities at some finite extraction radius. An understanding of finite radius corrections to {psi}{sub 4} and E allows us to more accurately infer their asymptotic values from a computation. In this paper, we show that, if the final state of the system is a black hole, then the leading correction to {psi}{sub 4} is O(1/r{sup 3}), and that to the energy flux is O(1/r{sup 4})--not O(1/r{sup 2}) and O(1/r{sup 3}), as one might naively guess. Our argument only relies on the behavior of the curvature scalars for black hole spacetimes. Using black hole perturbation theory, we calculate the corrections to the leading falloff, showing that it is quite easy to correct for finite extraction radius effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2010

Binary pulsar constraints on the parametrized post-Einsteinian framework

We constrain the parameterized post-Einsteinian framework with binary pulsar observations of orbital period decay due to gravitational wave emission. This framework proposes to enhance the amplitude and phase of gravitational waveform templates through post-Einsteinian parameters to search for generic deviations from general relativity in gravitational wave data. Such enhancements interpolate between general relativity and alternative theory predictions, but their magnitude must be such as to satisfy all current experiments and observations. The data that currently constrains the parameterized post-Einsteinian framework the most is the orbital period decay of binary pulsars. We use such observations to bound the magnitude of post-Einsteinian parameters, which will be critical when gravitational waves are detected and this framework is implemented.

79 ASTRONOMY AND ASTROPHYSICS↗