TITLE:   GCN CIRCULAR
NUMBER:  34582
SUBJECT: Subject: GRB230826A: Swift/UVOT upper limits
DATE:    23/08/28 10:21:42 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and R. A. J. Eyles-Ferris (U Leicester) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230826A 114 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 34565).
No optical afterglow consistent with the enhanced XRT position (Osborne et al., GCN Circ. 34569) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           114          263        147           >20.0
white              606         5452        312           >20.4
v                  657         1105         58           >17.8
b                  582         5339        255           >19.6
u                  327         5134        481           >19.5
uvw1               707         1320         71           >18.4
uvm2               682         1303         78           >18.4
uvw2               632         1254         78           >18.6

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.243 in the direction of the burst (Schlegel et al. 1998).