TITLE: GCN CIRCULAR NUMBER: 32998 SUBJECT: GRB 221201A: Swift detection of a burst DATE: 22/12/01 12:47:26 GMT FROM: Phil Evans at U of Leicester E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester), M. Ferro (INAF-OAB), J.D. Gropp (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 12:25:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 221201A (trigger=1142847). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 266.933, -68.260 which is RA(J2000) = 17h 47m 44s Dec(J2000) = -68d 15' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 40 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~-13 sec after the trigger. (The peak occurred during a pre-planned slew and the nominal trigger time is the start of the first post-slew image.) The XRT began observing the field at 12:27:56.2 UT, 170.6 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 266.9228, -68.2510 which is equivalent to: RA(J2000) = 17h 47m 41.47s Dec(J2000) = -68d 15' 03.6" with an uncertainty of 5.7 arcseconds (radius, 90% containment). This location is 35 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 0.1 s image was 2.34e-08 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 202 seconds with the U filter starting 337 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. Data from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.065. Burst Advocate for this burst is E. Troja (nora.gsfc AT gmail.com). 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/)