Relativistic tidal compressions of a star by a massive black hole
  Aims: We investigate the stellar pancake mechanism during which a solar-type
star is tidally flattened within its orbital plane passing close to a 10^6
solar masses black hole. We simulate the relativistic orthogonal compression
process and follow the associated shock waves formation.
  Methods: We consider a one-dimensional hydrodynamical stellar model moving in
the relativistic gravitational field of a non-rotating black hole. The model is
numerically solved using a Godunov-type shock-capturing source-splitting method
in order to correctly reproduce the shock waves profiles.
  Results: Simulations confirm that the space-time curvature can induce several
successive orthogonal compressions of the star which give rise to several
strong shock waves. The shock waves finally escape from the star and repeatedly
heat up the stellar surface to high energy values. Such a shock-heating could
interestingly provide a direct observational signature of strongly disruptive
star - black hole encounters through the emission of hard X or soft gamma-ray
bursts. Timescales and energies of such a process are consistent with some
observed events such as GRB 970815.
