Optical Afterglow Observations of the Unusual Short-Duration Gamma-Ray   Burst 040924
  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. 
K. Y. Huang, Y. Urata, A. V. Filippenko, J. H. Hu, W. H. Ip, P. H.   Kuo, W. Li, H. C. Lin, Z. Y. Lin, K. Makishima, K. Onda...