TITLE:   GCN CIRCULAR
NUMBER:  13138
SUBJECT: GRB 120327A: Swift/UVOT further analysis
DATE:    12/03/27 12:50:38 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

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).
A source consistent with the enhanced XRT position (Osborne et al.
GCN Circ. 13135) 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).

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).