LISA capture sources: Approximate waveforms, signaltonoise ratios, and parameter estimation accuracy
Abstract
Captures of stellarmass compact objects (COs) by massive (∼10^{6}M_{⊙}) black holes (MBHs) are potentially an important source for LISA, the proposed spacebased gravitationalwave (GW) detector. The orbits of the inspiraling COs are highly complicated; they can remain rather eccentric up until the final plunge, and display extreme versions of relativistic perihelion precession and LenseThirring precession of the orbital plane. The amplitudes of the strongest GW signals are expected to be roughly an order of magnitude smaller than LISA’s instrumental noise, but in principle (i.e., with sufficient computing power) the GW signals can be disentangled from the noise by matched filtering. The associated template waveforms are not yet in hand, but theorists will very likely be able to provide them before LISA launches. Here we introduce a family of approximate (postNewtonian) capture waveforms, given in (nearly) analytic form, for use in advancing LISA studies until more accurate versions are available. Our model waveforms include most of the key qualitative features of true waveforms, and cover the full space of captureevent parameters (including orbital eccentricity and the MBH’s spin). Here we use our approximate waveforms to (i) estimate the relative contributions of different harmonics (of the orbital frequency) to the total signaltonoise ratio, and (ii) estimate the accuracy with which LISA will be able to extract the physical parameters of the capture event from the measured waveform. For a typical source (a 10M_{⊙} CO captured by a 10^{6}M_{⊙} MBH at a signaltonoise ratio of 30), we find that LISA can determine the MBH and CO masses to within a fractional error of ∼10^{4}, measure S/M^{2} (where S and M are the MBH’s mass and spin) to within ∼10^{4}, and determine the location to the source on the sky to within ∼10^{3} stradians.
 Publication:

Physical Review D
 Pub Date:
 April 2004
 DOI:
 10.1103/PhysRevD.69.082005
 arXiv:
 arXiv:grqc/0310125
 Bibcode:
 2004PhRvD..69h2005B
 Keywords:

 04.80.Nn;
 04.25.Nx;
 04.30.Db;
 04.80.Cc;
 Gravitational wave detectors and experiments;
 PostNewtonian approximation;
 perturbation theory;
 related approximations;
 Wave generation and sources;
 Experimental tests of gravitational theories;
 General Relativity and Quantum Cosmology;
 Astrophysics
 EPrint:
 34 pages, 27 eps figures