  We present a detailed study of the spectral and temporal properties of the
X-ray and optical emission of GRB050713a up to 0.5 day after the main GRB
event. The X-ray light curve exhibits large amplitude variations with several
rebrightenings superposed on the underlying three-segment broken powerlaw that
is often seen in Swift GRBs. Our time-resolved spectral analysis supports the
interpretation of a long-lived central engine, with rebrightenings consistent
with energy injection in refreshed shocks as slower shells generated in the
central engine prompt phase catch up with the afterglow shock at later times.
Our sparsely-sampled light curve of the optical afterglow can be fitted with a
single power law without large flares. The optical decay index appears flatter
than the X-ray one, especially at later times.
