The early inspiral of massive stellar-mass black-hole binaries merging in LIGOs sensitivity band will be detectable at low frequencies by the upcoming space mission LISA. LISA will predict, with years of forewarning, the time and frequency with which
binaries will be observed by LIGO. We will, therefore, find ourselves in the position of knowing that a binary is about to merge, with the unprecedented opportunity to optimize ground-based operations to increase their scientific payoff. We apply this idea to detections of multiple ringdown modes, or black-hole spectroscopy. Narrowband tunings can boost the detectors sensitivity at frequencies corresponding to the first subdominant ringdown mode and largely improve our prospects to experimentally test the Kerr nature of astrophysical black holes. We define a new consistency parameter between the different modes, called $delta {rm GR}$, and show that, in terms of this measure, optimized configurations have the potential to double the effectiveness of black-hole spectroscopy when compared to standard broadband setups.
We propose a generic, phenomenological approach to modifying the dispersion of gravitational waves, independent of corrections to the generation mechanism. This model-independent approach encapsulates all previously proposed parametrizations, includi
ng Lorentz violation in the Standard-Model Extension, and provides a roadmap for additional theories. Furthermore, we present a general approach to include modulations to the gravitational-wave polarization content. The framework developed here can be implemented in existing data analysis pipelines for future gravitational-wave observation runs.
A frequentist asymptotic expansion method for error estimation is employed for a network of gravitational wave detectors to assess the amount of information that can be extracted from gravitational wave observations. Mathematically we derive lower bo
unds in the errors that any parameter estimator will have in the absence of prior knowledge to distinguish between the post-Einsteinian (ppE) description of coalescing binary systems and that of general relativity. When such errors are smaller than the parameter value, there is possibility to detect these violations from GR. A parameter space with inclusion of dominant dephasing ppE parameters $(beta, b)$ is used for a study of first- and second-order (co)variance expansions, focusing on the inspiral stage of a nonspinning binary system of zero eccentricity detectible through Adv. LIGO and Adv. Virgo. Our procedure is an improvement of the Cram{e}r-Rao Lower Bound. When Bayesian errors are lower than our bound it means that they depend critically on the priors. The analysis indicates the possibility of constraining deviations from GR in inspiral SNR ($rho sim 15-17$) regimes that are achievable in upcoming scientific runs (GW150914 had an inspiral SNR $sim 12$). The errors on $beta$ also increase errors of other parameters such as the chirp mass $mathcal{M}$ and symmetric mass ratio $eta$. Application is done to existing alternative theories of gravity, which include modified dispersion relation of the waveform, non-spinning models of quadratic modified gravity, and dipole gravitational radiation (i.e., Brans-Dicke type) modifications.
