TITLE:   GCN CIRCULAR
NUMBER:  41450
SUBJECT: GRB 250814A: Swift/UVOT Upper Limits
DATE:    25/08/20 15:20:29 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250814A 179 s after the BAT trigger (Caputo et al., GCN Circ. 41358). No optical afterglow consistent with the XRT position (Salvaggio et al., GCN Circ. 41379) 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

u_FC               179          429          246         >20.3
white              460         1537          264         >21.8
v                  510         1412           97         >20.2
b                  436         1511          117         >20.2
u                  179         1486          343         >20.5
w1                 560         1462           97         >19.5
m2                 708         1263           58         >18.6
w2                 486         1556          130         >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.066 in the direction of the burst
(Schlegel et al. 1998).