GCN Circular 42786
Subject
GRB 251118A: Swift/UVOT Detection
Event
Date
2025-11-20T22:23:37Z (15 hours ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251118A 31.3 ks after the Fermi trigger (GCN Circ. 42743). A fading source consistent with the XRT position (Osbourne et al., GCN Circ. 42782) is detected in the UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 10:14:01.01 = 160.00422 (deg.)
Dec (J2000) = -34:31:21.1 = -34.52254 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
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 31521 52651 885 18.79+/-0.05
white 108251 159027 1113 20.11+/-0.10
v 31678 42929 845 18.60+/-0.19
v 108564 147691 662 >19.73
u 31363 52627 2489 18.41+/-0.05
u 107942 158555 1113 19.61+/-0.15
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.057 in the direction of the burst
(Schlegel et al. 1998).