  In a galactic nucleus, a star on a low angular momentum orbit around the
central massive black hole can be fully or partially disrupted by the black
hole tidal field, lighting up the compact object via gas accretion. This
phenomenon can repeat if the star, not fully disrupted, is on a closed orbit.
Because of the multiplicity of stars in binary systems, also binary stars may
experience in pairs such a fate, immediately after being tidally separated. The
consumption of both the binary components by the black hole is expected to
power a double-peaked flare. In this paper, we perform for the first time, with
GADGET2, a suite of smoothed particle hydrodynamics simulations of binary stars
around a galactic central black hole in the Newtonian regime. We show that
accretion luminosity light curves from double tidal disruptions reveal a more
prominent knee, rather than a double peak, when decreasing the impact parameter
of the encounter and when elevating the difference between the mass of the star
which leaves the system after binary separation and the mass of the companion.
The detection of a knee can anticipate the onset of periodic accretion
luminosity flares if one of the stars, only partially disrupted, remains bound
to the black hole after binary separation. Thus knees could be precursors of
periodic flares, which can then be predicted, followed up and better modelled.
Analytical estimates in the black hole mass range $10^5-10^8 \rm M_{\rm \odot}$
show that the knee signature is enhanced in the case of black holes of mass
$10^6-10^7 \rm M_{\rm \odot}$.
