TITLE:   GCN CIRCULAR
NUMBER:  31482
SUBJECT: GRB 220117A: Swift/UVOT Upper Limits
DATE:    22/01/18 14:13:23 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of GRB 220117A 162 s after the BAT trigger 
(Melandri et al., GCN Circ. 31466).
No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 31472) 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           162          311          147         >20.5
u_FC               320          570          246         >20.0
white              162          998          306         >20.7
v                  650          845           39         >18.4
b                  576          770           39         >19.4
u                  320          744          265         >20.0
w1                 700          720           19         >19.3
m2                 675          869           39         >18.7
w2                 626          821           39         >18.9

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.028 in the direction of the burst (Schlegel et al. 1998).