TITLE: GCN CIRCULAR NUMBER: 41904 SUBJECT: GRB 250920C: Swift detection of a burst DATE: 25/09/20 15:39:55 GMT FROM: David Palmer at LANL <palmer@lanl.gov> R. Gupta (NASA GSFC), S. Dichiara (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 15:25:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250920C (trigger=1351039). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 51.459, -29.646 which is RA(J2000) = 03h 25m 50s Dec(J2000) = -29d 38' 44" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 40 sec. The peak count rate was ~8500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 15:27:21.2 UT, 123.8 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 51.4644, -29.6566 which is equivalent to: RA(J2000) = 03h 25m 51.46s Dec(J2000) = -29d 39' 23.8" with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 41 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 2.5 s image was 1.50e-09 erg cm^-2 s^-1 (0.2-10 keV). There are no UVOT data available at this time. Burst Advocate for this burst is R. Gupta (rahulbhu.c157 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/) View this GCN Circular online at https://gcn.nasa.gov/circulars/41904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...