TITLE:   GCN CIRCULAR
NUMBER:  41265
SUBJECT: GRB 250805A: Swift/UVOT Upper Limits
DATE:    25/08/07 12:47:42 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) and Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250805A
3536 s after the BAT trigger (Ambrosi et al., GCN Circ. 41233).
No optical afterglow consistent with the XRT position (Beardmore et al., 
GCN Circ. 41238) or optical afterglow (Izzo et al., GCN Circ. 41241; Li et
al., GCN Circ. 41241) 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          3536         3686          147         >21.3
white             3536         4306          344         >21.7
b                 3902         4101          197         >20.9
u                 3696         3895          197         >20.6
w2                4312         4460          146         >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.092 in the direction of the burst
(Schlegel et al. 1998).