GCN Circular 29787

Paul Kuin (MSSL/UCL) and A. Melandri(INAF-OAB) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210410A
(trigger 01042113; previously reported by Fermi/GBM in GCN #29777)
1113 s after the Fermi trigger at 2021-04-10 00:53:16 UT.
No optical afterglow consistent with the XRT position (Melandri et
al. GCN Circ. 29778
Not found
 
 
) 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 3-sigma UL

v                 1129         1149           19         >17.0
b                 5021         5109           85         >19.7
u                 4817         5014          197         >19.9
w1                4610         4809          197         >19.3
m2                4403         4602          197         >19.4
w2                1113         1125           12         >17.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).