GCN Circular 42554
Subject
GRB 251103A: Swift/UVOT Detection
Event
Date
2025-11-03T16:40:07Z (19 days ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
Via
email
A. A. Breeveld (UCL-MSSL) and S. Lanava (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of the SVOM/ECLAIRs detected burst GRB 251103A 4797s after the trigger (Hu et al., GCN Circ. 42534).
The optical counterpart detected by Schneider et al., GCN Circ. 42535; Turpin et al., GCN Circ. 42538; Gritsevich et al., GCN Circ. 42539; Izzo et al., GCN Circ. 42540, O'Neill et al., GCN Circ. 42543, Ghosh et al., GCN Circ. 42545, is detected in the initial U-band UVOT exposures, and is fading.
Preliminary magnitudes using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 4797 6349 1528 17.3 ± 0.04
u 9974 10188 211 17.9 ± 0.10
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.061 in the direction of the burst (Schlegel et al. 1998).