TITLE: GCN GRB OBSERVATION REPORT NUMBER: 484 SUBJECT: Refined IPN localization of GRB991216 DATE: 99/12/18 05:34:16 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the Ulysses GRB team, and M. Feroci, on behalf of the BeppoSAX GRB team, report: We have obtained a refined IPN annulus for GRB991216, approximately two times narrower than the one reported in the automated GCN/IPN/ Huntsville localization circulated earlier today. The annulus center is at RA(2000), Decl.(2000) = 346.505, +31.230, and the radius is 84.915 +/- 0.016 degrees (3 sigma). The annulus reduces the area of the RXTE error box reported in the GCN/RXTE_PCA burst position notice circulated earlier today, and its center line passes approximately 3 arcseconds from the optical transient position reported by Halpern et al. (GCN 472). This annulus can be refined further. Due to hacker activity, a map cannot be posted immediately on the IPN website. Contact khurley@sunspot.ssl.berkeley.edu for one.