  We numerically studied close encounters between a young stellar system
hosting a massive, gravitationally fragmenting disk and an intruder diskless
star with the purpose to determine the evolution of fragments that have formed
in the disk prior to the encounter. Numerical hydrodynamics simulations in the
non-inertial frame of reference of the host star were employed to simulate the
prograde and retrograde co-planar encounters. The initial configuration of the
target system (star plus disk) was obtained via a separate numerical simulation
featuring the gravitational collapse of a solar-mass pre-stellar core. We found
that close encounters can lead to the ejection of fragments that have formed in
the disk of the target prior to collision. In particular, prograde encounters
are more efficient in ejecting the fragments than the retrograde encounters.
The masses of ejected fragments are in the brown-dwarf mass regime. They also
carry away an appreciable amount of gas in their gravitational radius of
influence, implying that these objects may possess extended disks or envelopes,
as also suggested by Thies et al. (2015). Close encounters can also lead to the
ejection of entire spiral arms, followed by fragmentation and formation of
freely-floating objects straddling the planetary mass limit. However, numerical
simulations with a higher resolution are needed to confirm this finding.
