GCN Circular 28259
M. G. Bernardini (INAF-OAB) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift team: Using the full data set from recent downlinks, we report further ground data analysis for Swift trigger 990358 (Bernardini et al. GCN Circ. 28253). The BAT analysis uses data from T-61 to T+242 sec. The BAT image significance has now decreased to 4.4 sigma (15-350 keV). Also, the mask-weighted light curve does not show anything significant. Ground analysis of 1.7 ks of XRT PC mode data confirms that no XRT counterpart is detected in the BAT error circle. We thus conclude that this trigger was due to detector noise.