GCN Circular 45752
Subject
GRB 260925A: Swift/UVOT Upper Limits
Event
Date
2026-09-25T20:48:29Z (a day ago)
From
noelklin@umbc.edu
Via
Web form
N. Klingler (NASA-GSFC / UMBC / CRESST II) and E. Ambrosi (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 260925A 115 s after the BAT trigger (Ambrosi et al., GCN Circ. 45739). No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 45746) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 115 265 147 >20.0
u_FC 273 523 246 >19.1
white 115 1372 358 >20.9
v 603 1249 78 >17.9
b 529 1348 62 >18.2
u 273 1323 304 >19.3
w1 652 1299 55 >18.3
m2 1079 1099 19 >17.6
w2 578 771 39 >18.3
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998).