The Rapid Decay of the Optical Emission from GRB 980326 and Its Possible Implications
Piro, L.; Veilleux, S.; Pian, E.; Palazzi, E.; Greiner, J.; Frontera, F.; Galama, T. J.; Hurley, K.; Costa, E.; Böhm, A.; Lidman, C.; Kouveliotou, C.; Smith, R.; van Paradijs, J.; Tanvir, N.; Vreeswijk, P. M.; Wijers, R. A. M. J.; Groot, P. J.; Masetti, N.; Heise, J.; Stanek, K. Z.; Gorosabel, J.; Feroci, M.; Casares, J.; Castro-Tirado, A. J.; Fricke, K. J.; Garcia, M.; Bland-Hawthorn, J.; Covarrubias, R.; Jonker, P. G.; Gonzalez, J. -F.; Brown, W. R.; Jäger, K.; Hall, P.; Jones, B.; Robinson, C.; Briggs, M.; Zand, J. J. M. in't.; Tinney, C.; Keane, M.; Smith, M. G.; Windridge, D.
Netherlands, United Kingdom, Italy, United States, Australia, Chile, Canada, Spain, Germany
Abstract
We report the discovery of the optical counterpart to GRB 980326. Its rapid optical decay can be characterized by a power law with exponent -2.10+/-0.13 and a constant underlying source at Rc=25.5+/-0.5. Its optical colors 2.1 days after the burst imply a spectral slope of -0.66+/-0.70. The γ-ray spectrum as observed with BATSE shows that it is among the 4% softest bursts ever recorded. We argue that the rapid optical decay may be a reason for the nondetection of some low-energy afterglows of GRBs.