TITLE:   GCN CIRCULAR
NUMBER:  15414
SUBJECT: GRB 131030A: Swift/UVOT Detection
DATE:    13/10/31 11:46:48 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131030A 90 
s after the BAT trigger (Troja et al., GCN Circ. 15402). A fading source 
consistent with the XRT position (Troja et al. GCN Circ. 15402) is 
clearly detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  23:00:16.14 = 345.06723 (deg.)
     Dec (J2000) = -05:22:05.2  =  -5.36811 (deg.)
with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system (Breeveld et 
al. 2011, AIP Conf. Proc. 1358, 373) for the finding chart (FC) and 
other early exposures are:

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

white_FC            90          239          148         14.87 ± 0.02
white              582          601           20         16.13 ± 0.05
u_FC               302          552          246         15.30 ± 0.03
b                  557          577           20         16.30 ± 0.08
v                  631          651           19         15.98 ± 0.13
uvw1               681          701           19         16.42 ± 0.17
uvm2               656          676           20         16.63 ± 0.24
uvw2               606          626           20         17.97 ± 0.36

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.06 in the direction of the 
burst (Schlegel et al. 1998).