MG12 - Talk detail
 

Back to previous page

 Participant 

Institution

Session

Talk

Abstract

Transient resonances in the inspirals of point particles into black holes

We show that the two body problem in general relativity in the highly relativistic regime has a qualitatively new feature: the occurence of resonances. The resonances occur when the ratio of polar and radial orbital frequencies, which is slowly evolving under the influence of gravitational radiation reaction, passes through a low order rational number. The resonances make the orbit more sensitive to changes in the initial data, and are genuine non-perturbative effects that are not seen at any order in the standard post-Newtonian expansion used for two body systems at large separation. Our results directly apply to an important potential source of gravitational waves, namely the gradual inspiral of compact objects into much more massive black holes. Exploiting observations of these gravitational waves to map the spacetime geometry of black holes is contingent upon accurate theoretical models of the binary dynamics. At present, only the leading order in the mass ratio gravitational waveforms can be computed. Corrections to the waveform's phase due to the effects of transient resonances scale as the square root of the inverse of the mass ratio and are characterized by sudden jumps in the time derivatives of the phase. We numerically estimate the net size of these corrections and find indications that the phase error is of order a few cycles for mass ratios $\sim 10^{- 3}$ but will be significant (of order tens of cycles) for mass ratios $\sim 10^{-6}$. Computations of these corrections will require the computation of pieces of the forcing terms in the equations of motion which are currently unknown.

Constraining neutron star tidal Love numbers with gravitational wave detectors

Coalescing binary neutron stars are one of the most important sources for ground-based gravitational wave detectors. One of the key scientific goals of detecting the signal from such binaries is to obtain information about the nuclear equation of state, which is at present poorly constrained in the density range relevant to neutron star interiors. I will discuss the potential feasibility of obtaining robust constraints on the neutron star internal structure from gravitational wave observations with LIGO using data only from the early, low-frequency part of detected neutron star binary inspirals. In this adiabatic regime, the influence of a neutron star's internal structure is a small correction to the waveform's phase, but it is a relatively clean signature and depends only on a single parameter of the star related to its tidal Love number, namely, the ratio of the induced quadrupole moment to the perturbing tidal field, whose computation I will discuss for fully relativistic stars.

Back to previous page