Did GRB 970228 and GRB 970508 present similar optical properties?

Abstract

The analysis of the light curves of the optical counterparts of GRB 970228 and GRB 970508 points out remarkable similarities. The spectral distribution obtained from the color indices shows that both the transients became bluer during the increasing stage, and redder after the maximum. A main difference concerns the behaviour of the optical fading which is well fitted by a single power law in the case of GRB 970508 but not in the case of GRB 970228.