TITLE: GCN CIRCULAR NUMBER: 8537 SUBJECT: GRB 081121: Swift detection of a burst DATE: 08/11/21 20:48:42 GMT FROM: David Palmer at LANL S. R. Oates (UCL-MSSL), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Schady (MSSL-UCL), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), L. Vetere (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 20:35:32 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081121 (trigger=335105). Due to an Earth limb constraint slew could not immediately slew to this burst. The BAT on-board calculated location is RA, Dec 89.264, -60.626 which is RA(J2000) = 05h 57m 03s Dec(J2000) = -60d 37' 32" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single FRED structure with a duration of about 15 sec, with overlying spikes. There may be continued low-level emission out to 100 seconds. The peak count rate was ~4000 counts/sec (15-350 keV), at ~1.5 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+45.2 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)