TITLE: GCN CIRCULAR NUMBER: 11493 SUBJECT: Trigger 441015: Swift detection of a possible burst or transient DATE: 10/12/25 19:19:33 GMT FROM: Judith Racusin at GSFC J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester), S. Campana (INAF-OAB), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/IASFPA) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 18:37:45 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 101225A (trigger=441015). Swift slewed immediately to the burst. However, given that this was a 1088-second image trigger, the time from the trigger time (at the start of the image interval) to the XRT observation is over 23 minutes. The BAT on-board calculated location is RA, Dec 0.234, +44.602 which is RA(J2000) = 00h 00m 56s Dec(J2000) = +44d 36' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Since this was an image trigger, the currently available BAT light curve does not show significant structure. The XRT began observing the field at 19:00:48.5 UT, 1383.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 0.1992, +44.6017 which is equivalent to: RA(J2000) = 00h 00m 47.80s Dec(J2000) = +44d 36' 06.1" with an uncertainty of 5.1 arcseconds (radius, 90% containment). This location is 89 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. UVOT data products have not been received at this time. The BAT trigger was an unusually long image trigger. Due to the relative proximity to the Galactic plane (l=113.55,b=-17.35), and lack of fading information from XRT at this time, we are unsure if this trigger is a GRB or transient. We will report as more information is available. Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 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.)