TITLE:   GCN CIRCULAR
NUMBER:  31885
SUBJECT: GRB 220412A: Swift/UVOT Upper Limits
DATE:    22/04/12 16:20:20 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. Breeveld (UCL-MSSL) and N. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 220412A 127 s after the BAT trigger 
(Klingler et al., GCN Circ. 31881).
No optical afterglow consistent with the RATIR position (Watson et al., GCN Circ. 31882) 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) exposures and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           127          276          147         >20.5
u_FC               285          479          191         >19.6
white              566          758           34         >19.7
b                  542          734           34         >18.97
v                  616         1059           53         >18.18
uvw1               665          857           34         >18.25
uvw2               592         1039           58         >18.64
uvm2               813          833           20         >17.37


The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.0373 in the direction of the burst (Schlegel et al. 1998).