The discovery of an optical counterpart to GRB010222 (detected by BeppoSAX; Piro 2001) was announced 4.4 hrs after the burst by Henden (2001a). The Sloan Digital Sky Surveys 0.5m photometric telescope (PT) and 2.5m survey telescope were used to observe the afterglow of GRB010222 starting 4.8 hours after the GRB. The 0.5m PT observed the afterglow in five, 300 sec g band exposures over the course of half an hour, measuring a temporal decay rate in this short period of F_nu propto t^{-1.0+/-0.5}. The 2.5m camera imaged the counterpart nearly simultaneously in five filters (u g r i z), with r = 18.74+/-0.02 at 12:10 UT. These multicolor observations, corrected for reddening and the afterglows temporal decay, are well fit by the power-law F_nu propto nu^{-0.90+/-0.03} with the exception of the u band UV flux which is 20% below this slope. We examine possible interpretations of this spectral shape, including source extinction in a star forming region.
تحميل البحث