TITLE:   GCN CIRCULAR
NUMBER:  29764
SUBJECT: GRB 210402A: Swift/UVOT Upper Limits
DATE:    21/04/05 23:52:02 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210402A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and K. L. Page (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210402A
73 s after the BAT trigger (Page et al., GCN Circ. 29743).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 29750)
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           163          313          147         >20.8
u_FC               321          571          246         >20.3
white              163         1718          411         >21.4
v                  653         5581          229         >19.6
b                  578         1694          117         >20.2
u                  321         1669          304         >20.2
w1                1108         1644           78         >19.2
w2                1207         1227           19         >18.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.018 in the direction of the burst
(Schlegel et al. 1998).