TITLE:   GCN CIRCULAR
NUMBER:  23499
SUBJECT: GRB 181201A: Swift/UVOT Detection
DATE:    18/12/04 00:22:12 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 18201A
14.3 ks after the INTEGRAL trigger (Mereghetti et al., GCN Circ. 23469).
We confirm the optical afterglow initially reported by MASTER (Podeta et al.,
GCN Circ. 23470, Kong, GCN Circ. 23475, Volnova et al., GCN Circ. 23477, Mazaeva
et al., GCN Circ. 23479, Watson et al., GCN Circ. 23481, Belkin et al., GCN Circ.
23485, Bolmer and Schady, GCN Circ. 23486, Cai et al., GCN Circ. 23491). The 
position of the afterglow is also consistent with the XRT afterglow
(Page et al., GCN Circ. 23474). The detection of the afterglow in the uvw2
filter would be consistent with the redshift report by Izzy et al. (GCN Circ. 23488).

The preliminary UVOT position is:
  RA  (J2000) =  21:17:11.17 = 319.29656 (deg.)
  Dec (J2000) = -12:37:51.0  = -12.63084 (deg.)
with an estimated uncertainty of 0.2 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:

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

uvw2             14310        26435         4901       15.39 +/- 0.02
white            56416        74104          924       17.53 +/- 0.03
white           148341       165117         1162       18.71 +/- 0.04
v                56713        74204          535       17.70 +/- 0.10
v               160066       165389          389       18.70 +/- 0.26
u                56120        77881         2757       17.25 +/- 0.03
u               148114       164276         2896       18.30 +/- 0.05

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).