  We present numerical simulations of circumbinary accretion onto eccentric and
circular binaries using the moving-mesh code AREPO. This is the first set of
simulations to tackle the problem of binary accretion using a finite-volume
scheme on a freely moving mesh, which allows for accurate measurements of
accretion onto individual stars for arbitrary binary eccentricity. While
accretion onto a circular binary shows bursts with period of ~5 times the
binary period P_b,accretion onto an eccentric binary is predominantly modulated
at the period ~1P_b. For an equal-mass circular binary, the accretion rates
onto individual stars are quite similar to each other, following the same
variable pattern in time. By contrast, for eccentric binaries, one of the stars
can accrete at a rate 10-20 times larger than its companion. This "symmetry
breaking" between the stars, however, alternates over timescales of order 200
P_b, and can be attributed to a slowly precessing, eccentric circumbinary disk.
Over longer timescales, the net accretion rates onto individual stars are the
same, reaching a quasi-steady state with the circumbinary disk. These results
have important implications for the accretion behavior of binary T-Tauri stars
and supermassive binary black holes.
