GCN Circular 11812

M. H. Siegel (PSU), S. T. Holland (CRESST/USRA/GSFC) and A. Melandri  
(INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 110319A
65s after the BAT trigger (Melandri et al, GCN Circ 11807
Not found
 
 
). We identify
an optical afterglow near the enchanced XRT position given by Melandri
et al. (GCN Circ. 11810
Not found
 
 
).  The transient is only detected in the optical
filters and shows fading between the first and second orbits.

The preliminary UVOT position is:

     RA (J2000)  23:46:00.69  =  356.50287 (deg)
    Dec (J2000) -66:00:40.4   =  -66.01122 (deg)

with an estimated uncertainty of 0.44 arcsec (radius, 90% confidence,
statistical + systematic).  Preliminary 3-sigma upper limits and  
magnitudes
using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627)  
for the
exposures are:

Filter    T_start(s) T_stop(s)  Exp(s)   Mag
white (fc)      65      215    147     18.36+-0.07
white         3924     5560    393     20.32+-0.22
v             4336     5971    393    >19.56
b             3719     5355    393     19.51+-0.21
b            11317    11950    615    >20.63
u              277      395    115     18.13+-0.13
u             4950    11310   1081     19.76+-0.18
uvw1          4745     4945    196    >19.72
uvw1          9497    10397    885    >20.58
uvm2          4540     4740    196    >19.64
uvm2          5976     6172    193    >19.69
uvw2          4131     4330    196    >19.91
uvw2          5566     5766    196    >19.91

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).