TITLE:   GCN CIRCULAR
NUMBER:  42554
SUBJECT: GRB 251103A: Swift/UVOT Detection
DATE:    25/11/03 16:40:07 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

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).