GCN Circular 19037

M. De Pasquale (MSSL-UCL) and J. Cummings (GSFC/UMBC) report
on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160220B
3.33 ks after the BAT trigger (Cummings et al., GCN Circ. 19029
Not found
 
 
).
No optical afterglow consistent with the XRT position (Evans et al.
GCN Circ. 19033
Not found
 
 
) is detected in the UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the
summed UVOT exposures are:

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

white             3735         5370          393         >21.0
v                 4145        10454         1082         >20.1
b                 3530         5165          393         >20.4
u                 4882        16950          451         >20.1

w1                4555        16884         1504         >20.9
m2                4350        11207          933         >20.7
w2                5499        32840         1170         >20.9

We note the presence of an uncatalogued source of magnitude 20.2 +/- 0.20
in white filter, at coordinates RA = 17h 19m 28.07, Dec = -18d 07m 25.5s
(J2000), which is 5" from the enhanced XRT position.

The magnitudes above are not corrected for the substantial Galactic 
extinction
due to the reddening of E(B-V) = 0.32 in the direction of the burst
(Schlegel et al. 1998).

-- 

Dr. Massimiliano De Pasquale
Research associate - Swift UVOT scientist
Mullard Space Science Laboratory, University College London