TITLE:   GCN CIRCULAR
NUMBER:  16890
SUBJECT: GRB 141004A: Swift/UVOT Detection
DATE:    14/10/05 16:07:41 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and V. D'Elia (ASDC) report on behalf of
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 141004A
65 s after the BAT trigger (D'Elia et al., GCN Circ. 16878).The GRB was
also detected by Integral (Mereghetti et al, GCN Circ. 16879), and in the
optical by CAHA (Gorosabel et al, GCN Circ. 16880), TNG (D'Elia et al.,
GCN Circ. 16881), at Monte Agliale Observatory (Ciabatta et al. GCN Circ.
16886) and by RATIR (Littlejohns et al., GCN Circ. 16887).  A source
consistent with the XRT position (Osborne et al. GCN Circ. 16883)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:06:56.14 =  76.73393 (deg.)
    Dec (J2000) = +12:49:11.3  =  12.81981 (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               65          215          147         17.64 +/- 0.07
v                  606         1922          156         18.94 +/- 0.24
b                  532         1156           58         18.94 +/- 0.20
u                  277          527          246         17.93 +/- 0.09
w1                 656         1453           97         18.67 +/- 0.24
m2                 806         7273          216        >20.5
w2                 582        13683          582         20.69 +/- 0.35

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.32 in the direction of the burst
(Schlegel et al. 1998).