  We report the discovery of a transient and fading hard X-ray emission in the
BATSE lightcurves of a sample of short gamma-ray bursts. We have summed each of
the four channel BATSE light curves of 76 short bursts to uncover the average
overall temporal and spectral evolution of a possible transient signal
following the prompt flux. We found an excess emission peaking ~30 s after the
prompt one, detectable for ~100 s. The soft power-law spectrum and the
time-evolution of this transient signal suggest that it is produced by the
deceleration of a relativistic expanding source, as predicted by the afterglow
model.
