TITLE:   GCN CIRCULAR
NUMBER:  29868
SUBJECT: GRB 210419C: Swift/UVOT Upper Limits
DATE:    21/04/21 16:30:59 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and M. J. Moss (GWU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210419C
156 s after the BAT trigger (Moss et al., GCN Circ. 29834).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 29839)
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           156          305          147         >20.83
white             6954        17801          254         >21.14
v                11428        28719          155         >19.22
b                 6749        17713         1081         >21.37
u                  313          408           93         >19.55
u                 6544        22974          258         >20.20
UVW1              6339        22905         1082         >20.49
UVM2              6134         6334          196         >19.21
UVW2             10522        28626         1771         >20.84

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.010 in the direction of the burst
(Schlegel et al. 1998).