GCN Circular 41291
Subject
GRB 250807A: Swift/UVOT Detection
Event
Date
2025-08-08T16:24:35Z (10 days ago)
From
s.shilling@lancaster.ac.uk
Via
Web form
S. P. R. Shilling (Lancaster U.) and N. J. Klingler (GSFC/UMBC/CRESSTII)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250807A
111 s after the BAT trigger (Klingler et al., GCN Circ. 41262).
A source consistent with the enhanced XRT position
(Evans et al., GCN Circ. 41270) is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 111 261 147 18.00 +/- 0.04
v 653 1769 136 >18.8
b 579 1695 117 >19.5
u 323 1840 361 19.88 +/- 0.31
w1 702 1818 117 >19.0
w2 801 821 19 >17.7
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.011 in the direction of the burst
(Schlegel et al. 1998).