TITLE:   GCN CIRCULAR
NUMBER:  31204
SUBJECT: GRB 211207A: Swift/UVOT Detection
DATE:    21/12/11 16:03:37 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 211207A
85 s after the BAT trigger (Ambrosi et al., GCN Circ. 31182).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 31184)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  09:58:29.79 = 149.62412 (deg.)
    Dec (J2000) = -24:21:31.3  = -24.35869 (deg.)
with an estimated uncertainty of 0.43 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               85          234          147         17.52 +/- 0.04
v                  627         1595          117        >18.5
b                  553          743           36         19.08 +/- 0.31
u                  297          546          246         18.15 +/- 0.09
w1                 677         1470           97        >18.7
m2                 652         1272           39        >18.7
w2                 776         1570           78        >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.050 in the direction of the burst
(Schlegel et al. 1998).