TITLE:   GCN CIRCULAR
NUMBER:  30528
SUBJECT: GRB 210723A: Swift/UVOT Upper Limits
DATE:    21/07/27 06:16:48 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210723A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and Sbarrato (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210723A
99 s after the BAT trigger (Sbarrato et al., GCN Circ. 30485).
No optical afterglow consistent with the XRT position
(Evans GCN Circ. 30486)
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            99          249          147         >20.6
u_FC               312          562          246         >19.2
white               99         1364          369         >20.6
v                  641         1241           78         >18.2
b                  567         1339           78         >19.3
u                  312         1315          304         >19.4
w1                 691         1290           58         >19.0
m2                 666         1266           78         >18.8
w2                 617         1217           78         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.962 in the direction of the burst
(Schlegel et al. 1998).