GCN Circular 13864

S. T. Holland (STScI) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121011A 109 s after
the BAT trigger (Racusin et al., GCN Circ. 13845
Not found
 
 
).  A source consistent with the
XRT position (Evans et al. GCN Circ. 13850
Not found
 
 
) is detected in the initial UVOT
exposures.

The preliminary UVOT position is:
    RA  (J2000) =  17:20:51.23 = 260.21346 (deg.)
    Dec (J2000) = +41:06:37.1  = +41.11030 (deg.)
with an estimated uncertainty of 0.52 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              109          258          147         18.96 +/- 0.06
v                 4093         5729          393         19.81 +/- 0.21
b                 3476         3676          197         19.51 +/- 0.18
u                 4708         4908          197         19.67 +/- 0.18
w1                4503        15916         1183        >20.9
m2                4298         5933          393        >22.6
w2                3888         5524          393        >21.0

The magnitudes in the table 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).