GCN Circular 14092

S. R. Oates (MSSL-UCL) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121217A
73 s after the BAT trigger (Siegel et al., GCN Circ. 14089
Not found
 
 
).
A source consistent with the GROND optical position (Elliott et al. GCN Circ. 14091
Not found
 
 
)
is detected in the initial UVOT exposures. The preliminary UVOT position is: 

    RA (J2000) = 10:14:50.32 = 153.7097  (deg)
   Dec (J2000) = -62:21:03.3 = -62.35096 (deg)

with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

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

white               73          222          147         19.58 +/- 0.13
v                  616         5906          313         19.01 +/- 0.22
b                  541          560          19          18.76 +/- 0.36
u                  285         6522          540         20.09 +/- 0.34
w1                 666         6317          313        >19.96
m2                 641         6112          313        >19.85
w2                 591         7138          510        >20.37

The magnitudes in the table are not corrected for the significant Galactic extinction
due to the reddening of E(B-V) = 0.37 in the direction of the burst
(Schlegel et al. 1998).