GCN Circular 29213

M. H. Siegel (PSU) and B. Sbarufatti (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 201229A
117 s after the BAT trigger (Sbarufatti et al., GCN Circ. 29192
Not found
 
 
).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 29193
Not found
 
 
) is detected in the initial UVOT exposures, consistent
with the optical transient reported in the initial circular and confirmed by
SAO (Moskvitin et al., GCN Circ. 29203
Not found
 
 
) and AbAO (Pankov et al., GCN Circ. 29205
Not found
 
 
).

The preliminary UVOT position is:
    RA  (J2000) =  14:02:45.40 = 210.68916 (deg.)
    Dec (J2000) = +48:11:53.3  =  48.19814 (deg.)
with an estimated uncertainty of 0.44 arc sec. (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 (fc)         117          266          147      18.22 +/- 0.05
white              555          749           38      18.50+/-0.13
white              879         1029          147      19.17+/-0.13
white             1182         1548           58      19.42+/-0.34
white            23280        24102          801      20.88+/-0.22
v                  605         1597          116     >18.48
v                17146        34853         1217     >20.39
b                  531         1523           97     >19.33
b                22367        23274          885     >21.24
u (fc)             275          525          245      18.13+/-0.09
u                  680         5086          107      18.57+/-0.25
u                12362        29756         1220      20.54+/-0.34
uvw1               654         5071          254      19.04+/-0.25
uvw1             28021        28921          885     >20.45
uvw2             16239        34408         1771      20.27+/-0.21

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).