GCN Circular 42354
Subject
GRB 251016A: Swift/UVOT Detection
Event
Date
2025-10-18T12:05:09Z (8 days ago)
From
s.shilling@lancaster.ac.uk
Via
Web form
S.P.R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251016A,
detected by SVOM/ECLAIRs (Basa et al., GCN Circ. 42308) and Fermi/GBM
(Fermi GBM team, GCN Circ. 42309), 6.66 ks after the SVOM/ECLAIRs trigger.
A source is detected in the optical by the Swift/UVOT at a position that is
consistent with the likely X-ray counterpart detected by the Swift/XRT
(Source 1: Evans et al., GCN Circ. 42311).
Preliminary detections and upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the images are:
Filter T_start(ks) T_stop(ks) Exp(s) Mag
u 6.66 12.6 491.7 19.13 +/- 0.26
b 6.91 12.7 296.0 18.70 +/- 0.18
v 7.42 7.67 245.8 17.52 +/- 0.15
w1 12.1 12.4 245.8 >18.93
w2 7.17 7.42 245.8 >19.05
m2 7.68 7.85 168.3 >18.66
The magnitudes reported here are not corrected for Galactic extinction.