  The 1-m telescope at Lulin Observatory and the 0.76-m Katzman Automatic
Imaging Telescope at Lick Observatory were used to observe the optical
afterglow of the short-duration (1.2--1.5 s) gamma-ray burst (GRB) 040924. This
object has a soft high-energy spectrum, thus making it an exceptional case,
perhaps actually belonging to the short-duration tail of the long-duration
GRBs. Our data, combined with other reported measurements, show that the early
R-band light curve can be described by two power laws with index alpha = -0.7
(at t = 16-50 min) and alpha = -1.06 (at later times). The rather small
difference in the spectral indices can be more easily explained by an afterglow
model invoking a cooling break rather than a jet break.
