TITLE:   GCN CIRCULAR
NUMBER:  41728
SUBJECT: GRB 250905A: Swift/UVOT Upper Limits
DATE:    25/09/05 20:04:34 GMT
FROM:    Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>

S. R. Oates (Lancaster Uni.) and R. Brivio (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250905A
140 s after the BAT trigger (Brivio et al., GCN Circ. 41714).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 41722)
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/3sigUL
white  (FC)     140          290             147           >21.0
   u    (FC)     300           405            103            >19.8
   v              4973       16058          1082            >20.3
   b              5794         5978            181            >20.3
   u              5588       27905          1036            >21.1
uvw1          5383       27038           1082           >20.4
uvm2          5178       16867            989            >20.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.054 in the direction of the burst
(Schlegel et al. 1998).