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Abstract We analyze accretion-rate time series for equal-mass binaries in coplanar gaseous disks spanning a continuous range of orbital eccentricities up to 0.8 for both prograde and retrograde systems. The dominant variability timescales match those of previous investigations; the binary orbital period is dominant for prograde binaries withe≳ 0.1, with a 5 × longer “lump” period taking over fore≲ 0.1. This lump period fades and drops from 5 × to 4.5 × the binary period aseapproaches 0.1, where it vanishes. For retrograde orbits, the binary orbital period dominates ate≲ 0.55 and is accompanied by a 2 × longer timescale periodicity at higher eccentricities. The shape of the accretion-rate time series varies with binary eccentricity. For prograde systems, the orientation of an eccentric disk causes periodic trading of accretion between the binary components in a ratio that we report as a function of binary eccentricity. We present a publicly available tool,binlite, that can rapidly (≲0.01 s) generate templates for the accretion-rate time series onto either binary component for choice of binary eccentricity below 0.8. As an example use case, we build lightcurve models where the accretion rate through the circumbinary disk and onto each binary component sets contributions to the emitted specific flux. We combine these rest-frame, accretion-variability lightcurves with observer-dependent Doppler boosting and binary self-lensing. This allows a flexible approach to generating lightcurves over a wide range of binary and observer parameter space. We envisionbinliteas the access point to a living database that will be updated with state-of-the-art hydrodynamical calculations as they advance. 

Abstract We have performed numerical calculations of a binary interacting with a gas disk, using 11 different numerical methods and a standard binary−disk setup. The goal of this study is to determine whether all codes agree on a numerically converged solution and to determine the necessary resolution for convergence and the number of binary orbits that must be computed to reach an agreed-upon relaxed state of the binary−disk system. We find that all codes can agree on a converged solution (depending on the diagnostic being measured). The zone spacing required for most codes to reach a converged measurement of the torques applied to the binary by the disk is roughly 1% of the binary separation in the vicinity of the binary components. For our disk model to reach a relaxed state, codes must be run for at least 200 binary orbits, corresponding to about a viscous time for our parameters, 0.2(a²Ω_B/ν) binary orbits, whereνis the kinematic viscosity. The largest discrepancies between codes resulted from the dimensionality of the setup (3D vs. 2D disks). We find good agreement in the total torque on the binary between codes, although the partition of this torque between the gravitational torque, orbital accretion torque, and spin accretion torque depends sensitively on the sink prescriptions employed. In agreement with previous studies, we find a modest difference in torques and accretion variability between 2D and 3D disk models. We find cavity precession rates to be appreciably faster in 3D than in 2D.