GCN Circular 13138

N. P. M. Kuin (MSSL-UCL) and B. Sbarufatti (INAF-OAB/PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120327A
141 s after the BAT trigger (Sbarufatti et al., GCN Circ. 13123
Not found
 
 
).
A source consistent with the enhanced XRT position (Osborne et al.
GCN Circ. 13135
Not found
 
 
) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  16:27:27.48  = 246.864500 (deg.)
   Dec (J2000) = -29:24:53.74  = -29.414928 (deg.)
with an estimated uncertainty of 0.48 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

v                  448          468           20         15.68 +/- 0.10
b                  396          416           20         16.97 +/- 0.11
u                  141          391          246         18.02 +/- 0.08
w1                 497         1295           97        >19.0
m2                 622         1271           78        >19.2
w2                 424         1222           97        >19.6

The absence of detection in uvw1, uvm2, and uvw2 is consistent with the
reported redshift of 2.81 (Perley & Tanvir, GCN Circ 13133, and
Krueler et al, GCN Circ. 13134
Not found
 
 
).

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.34 in the direction of the burst
(Schlegel et al. 1998).