Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session S10: Gravitational Waves Sources for LISA |
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Sponsoring Units: GGR DAP Chair: Richard Price, University of Texas at Brownsville Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis A |
Monday, April 14, 2008 1:30PM - 1:42PM |
S10.00001: The Mock LISA Data Challenges: status, achievements, and prospects Michele Vallisneri The Mock LISA Data Challenges are a program to demonstrate and encourage the development of data-analysis capabilities for LISA, the planned NASA--ESA space-based gravitational-wave detector. Each round of challenges consists of several data sets containing simulated instrument noise and gravitational waves from sources of undisclosed parameters. Participants are asked to analyze the data sets and report the maximum information they can infer about the source parameters. The challenges are being released in rounds of increasing complexity and realism, and so far they have already demonstrated the recovery of model signals from nonspinning supermassive black-hole binaries, from $\sim 20,000$ overlapping Galactic white-dwarf binaries, and from the extreme--mass-ratio inspirals of compact objects into central galactic black holes. Challenge 3, currently in progress, includes signals from spinning supermassive black-hole inspirals, from cosmic-string cusps, and from primordial stochastic backgrounds. We discuss the status, achievements, and prospects of the Challenges. [Preview Abstract] |
Monday, April 14, 2008 1:42PM - 1:54PM |
S10.00002: Inspirals of point particles into black holes via two-timescale Tanja Hinderer, Eanna Flanagan The inspiral of stellar mass compact objects into massive black holes are an important source for future gravitational wave detectors such as LISA and Advanced LIGO. Detection of these sources and extracting information from the signal relies on accurate theoretical models of the binary dynamics. We analyze this problem using a two-timescale expansion, which provides a rigorous derivation of the prescription for computing the leading order waveform. As shown by Mino, this leading order waveform, which we call the adiabatic waveform, requires only the radiative self force. The two-timescale method also lays the foundations for calculating the post-adiabatic corrections needed for measurement templates. We show that the leading order post-adiabatic corrections (terms in the phase that scale as the square root of the mass ratio) are due to transient resonances that occur during an inspiral when the ratio of the radial and azimuthal frequencies is a low order rational number. This effect is not seen in post-Newtonian expansions. At the next, subleading order (order unity terms in the phase), there are phase corrections due to the conservative and dissipative pieces of the first order self force, and the dissipative piece of the second order self force. The resonant phase shifts depend on the subleading order terms. Therefore, going beyond the adiabatic approximation would require computation of the dissipative piece of the second order self force. [Preview Abstract] |
Monday, April 14, 2008 1:54PM - 2:06PM |
S10.00003: Gravitational waves from extreme mass ratio inspirals: Preliminary results from a hybrid approach to generate adiabatic waveforms Pranesh Sundararajan, Gaurav Khanna, Scott Hughes, Steve Drasco Extreme mass ratio inspirals (in which a stellar mass compact object perturbs a massive black hole spacetime) are an important source of gravitational radiation. We present preliminary results from a hybrid time-frequency domain approach to solve the Teukolsky perturbation equation and thus generate adiabatic waveforms from such inspirals. Recently, we have developed a code which treats the Teukolsky equation as a (2+1) PDE and solves it in the time domain. The key feature of this code is its ability to generate waveforms corresponding to any spacetime trajectory of the point-like compact object. A Fourier decomposition of the Teukolsky equation is possible when the compact object is constrained to a bound geodesic. The radiated fluxes from such a Fourier mode based frequency-domain code can be used to construct an adiabatic inspiral trajectory for the smaller object. Combining the accuracy of this frequency-domain trajectory with the versatility of the time-domain code allows us to generate adiabatic waveforms. [Preview Abstract] |
Monday, April 14, 2008 2:06PM - 2:18PM |
S10.00004: The spectral signature of extreme mass ratio inspirals Steve Drasco I describe the spectral signature of adiabatic inspirals of stellar mass compact objects into much larger rotating black holes. Simulated spectral snapshots of these systems (valid for a fraction of expected observation times, but for many orbit cycles) are generally composed of lines that can be grouped into around ten families defined by fixing two of the orbit's three integer frequency multipliers. These mode families are fairly easy to predict from the geometry of the orbit, and inspiral simulations suggest that they are essentially fixed throughout the course of an inspiral. A hypothetical detection algorithm that tracks mode families dominating the first twelve hours of an inspiral would capture 98\% of the total power over the remaining three years before merger. I will discuss the observation potential for simplistic detection schemes which are designed around these results and which are capable of recovering the adiabatic evolution of the inspiral's orbit geometry. [Preview Abstract] |
Monday, April 14, 2008 2:18PM - 2:30PM |
S10.00005: Math for Mapping Spacetime Jeandrew Brink One of the important science objectives for LISA is to quantitatively map the strong field regions around compact objects using Extreme-Mass-Ratio Inspirals (EMRIs). While this idea has been shown to be possible in principle, in practice only inspirals in a Kerr spacetime have been studied in detail. A spacetime mapping algorithm for an EMRI inspiral into generic compact object is formulated using ideas from integrable systems. Aspects of theoretical development required to make a mathematical spacetime mapping machine an implementable reality are discussed. [Preview Abstract] |
Monday, April 14, 2008 2:30PM - 2:42PM |
S10.00006: Estimating the computational efficiency of frequency-- and time--domain calculations of gravitational waveforms from EMRIs Jonathan L. Barton, David J. Lazar, Gaurav Khanna, Daniel J. Kennefick, Lior M. Burko We estimate the computation time for the frequency-domain (FD) calculation of gravitational-wave fluxes and waveforms for EMRIs modeling a compact object in an equatorial orbit around a super-massive black hole. We determine the number of $k$ modes (associated with harmonics of the orbital radial frequencies) necessary to achieve a desired accuracy for each $m$ mode (associated with harmonics of the azimuthal frequencies) for orbits of varying eccentricity. We then model the time required to compute single $k$ modes and then find the computation time to sum over all the $k$ modes for a given accuracy level. Next, we compute the energy flux and the waveform in the time domain (TD), and estimate the computation time required to achieve the same accuracy level for the same orbital parameters, and estimate the parts of the parameter space for which the TD approach becomes computationally more efficient than the FD method. We plan to extend this study also to non-equatorial and finally generic Kerr orbits. [Preview Abstract] |
Monday, April 14, 2008 2:42PM - 2:54PM |
S10.00007: Black hole quasi-normal mode spectroscopy with LISA Manish M. Jadhav, Lior M. Burko We present an improved estimate of the signal-to-noise ratio (SNR) for the gravitational waves from the ring-down phase of coalescing black hole binaries for the NASA/ESA space- borne mission LISA. The usual all-sky average assumption is relaxed. We replace the usual averages of the spin-weighted spheroidal harmonics and physical and geometrical variables by Monte Carlo values, that are computed randomly for detector---source directions, black hole orientations, polarization state, phases, etc. E.g., for a given ``radiation efficiency" $\epsilon_{\rm rd}$ we use a randomly generated ``radiation efficiency per polarization state" $\epsilon^{+,\times}$, that reflects our ignorance of the polarization state of a typical source. We then estimate the non--angle--averaged, polarization and phase dependent SNR for both Schwarzschild and Kerr black holes, and determine by how much they differ from their all--sky averages as a function of the population sizes. [Preview Abstract] |
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