  An interaction between a star-disc system and another star will perturb the
disc, possibly resulting in a significant modification of the disc structure
and its properties. It is still unclear if such an encounter can trigger
fragmentation of the disc to form brown dwarfs or gas giant planets. This paper
details high resolution Smoothed Particle Hydrodynamics (SPH) simulations
investigating the influence of stellar encounters on disc dynamics. Star-star
encounters (where the primary has a self-gravitating, marginally stable
protostellar disc, and the secondary has no disc) were simulated with various
orbital parameters to investigate the resulting disc structure and dynamics.
This work is the first of its kind to incorporate realistic radiative transfer
techniques to realistically model the resulting thermodynamics.
  The results suggest that the effect of stellar encounters is to prohibit
fragmentation - compressive and shock heating stabilises the disc, and the
radiative cooling is insufficient to trigger gravitational instability. The
encounter strips the outer regions of the disc (either through tidal tails or
by capture of matter to form a disc around the secondary), which triggers a
readjustment of the primary disc to a steeper surface density profile (and a
flatter Toomre Q profile). The disc around the secondary plays a role in the
potential capture of the secondary to form a binary. However, this applies only
to orbits that are parabolic - hyperbolic encounters do not form a secondary
disc, and are not captured.
