We propose, within the effective-one-body approach, a new, resummed analytical representation of the gravitational-wave energy flux absorbed by a system of two circularized (nonspinning) black holes. This expression is such that it is well-behaved in the strong-field, fast-motion regime, notably up to the effective-one-body-defined last unstable orbit. Building conceptually upon the procedure adopted to resum the multipolar asymptotic energy flux, we introduce a multiplicative decomposition of the multipolar absorbed flux made by three factors: (i) the leading-order contribution, (ii) an “effective source” and (iii) a new residual amplitude correction $({\tilde{\rho }}_{\ell m}^H{)}^{2\ell }$. In the test-mass limit, we use a frequency-domain perturbative approach to accurately compute numerically the horizon-absorbed fluxes along a sequence of stable and unstable circular orbits, and we extract from them the functions ${\tilde{\rho }}_{\ell m}^H$. These quantities are then fitted via rational functions. The resulting analytically represented test-mass knowledge is then suitably hybridized with lower-order analytical information that is valid for any mass ratio. This yields a resummed representation of the absorbed flux for a generic, circularized, nonspinning black-hole binary. Our result adds new information to the state-of-the-art calculation of the absorbed flux at fractional 5 post-Newtonian order [S. Taylor and E. Poisson, Phys. Rev. D 78, 084016 (2008)], which is recovered in the weak-field limit approximation by construction.

• Received 13 December 2011

DOI:https://doi.org/10.1103/PhysRevD.85.044025