TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1172 SUBJECT: Detection of the X-ray afterglow of GRB011121 by BeppoSAX DATE: 01/12/03 12:39:11 GMT FROM: SAX Science Operations at IAS/CNR Frascati Detection of the X-ray afterglow of GRB011121 by BeppoSAX L. Piro, P. Soffitta (IAS/CNR-Rome), L.A. Antonelli (OAR-Roma), J. in 't Zand, J. Heise (SRON, Utrecht), L. Nicastro (IFCAI/CNR, Palermo), L. Amati (ITeSRE/CNR, Bologna), F. Frontera, C. Guidorzi, E. Montanari (Ferrara Univ.), L. Reboa (BeppoSAX SDC, Telespazio, ROma), M. Corsi, S. Granata (BeppoSAX SOC, Roma), G. Gennaro (BeppoSAX OCC, Roma), S. Rebecchi (ASI SDC, Roma), L. Salotti (ASI, Roma) We have successfully performed a follow-up observation of GRB011121 with BeppoSAX starting on Nov.22, 16.01 UT. This is the first TOO (Target of Opportunity) observation of a GRB after the new gyroless mode was installed in October and being tested. We have detected the fading X-ray afterglow of GRB011121 with NFI (1SAX J113426-7601.4) at a position RA(2000)= 11h34m25.8s, Decl(2000)=-76 01' 22", with an error radius of 50". This position is 25" away from the optical transient (GCN#1150), well within the error, verifying the good quality of the aspect reconstruction in this new pointing mode. A detailed data analysis is in progress.glow of GRB011121 with NFI (1SAX J113426-7601.4) at a position RA(2000)= 11h34m25.8s, Decl(2000)=-76 01' 22", with an error radius of 50". This position is 25" away from the optical transient (GCN#1150), well within the error, verifying the good quality of the aspect reconstruction in this new pointing mode. A detailed data analysis is in progress.