Spin Taylor F2

In coming years, gravitational wave detectors should find black hole-neutron star binaries, potentially coincident with astronomical phenomena like short GRBs. These binaries are expected to precess. Precessing black hole binaries produce a complicated signal, different in each direction, that reflects how the orbital plane precesses and the relative orientation of the line of sight and that precessing plane. Gravitational wave science requires a tractable model for precessing binaries, to disentangle precession physics from other phenomena like modified strong field gravity, tidal deformability, or Hubble flow; and to measure compact object masses, spins, and alignments.
Moreover, current searches for gravitational waves from compact binaries use templates where the binary does not precess and are ill-suited for detection of generic precessing sources.

In our paper, Andy Lundgren and I refactor existing expressions to provide a compact, accurate, intuitive expression for this precession, both as a function of time and a function of gravitational wave frequency. These analytic expressions enable previously-intractable analytic calculations like the Fisher matrix: a way of characterizing how similar neighboring signals are to one another and hence how well measurements can distinguish between them.

Our analysis provides an accessible foundation for the detection and interpretation of gravitational waves from generic compact binaries.

For experts By expressing the gravitational wave signal in radiation-frame coordinates, restricted to one line of sight, several authors following our work (e.g., Klein et al) have artificially introduced unnecessary coordinate-dependent complexity to the precessing gravitational wave signal. Our expressions are compact, correct, build on prior work, and enable new insight and calculations.

For more information, see

• Lundgren and O’Shaughnessy, arxiv:1304.3332 submitted to PRL

• Brown, Lundgren, and O’Shaughnessy PRD 86 4020 (2012) : A previous work easily explained using our simple result.