GCN Circular 21415

S. R. Oates (U. Warwick) and A. Cholden-Brown (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170804A
132 s after the BAT trigger (Cholden-Brown et al., GCN Circ. 21410
Not found
 
 
).

A fading source consistent with the XRT position
(Evans et al., GCN Circ. 21413
Not found
 
 
) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =   0:25:34.29 =   6.39288 (deg.)
     Dec (J2000) = -64:47:03.1  = -64.78419 (deg.)

with an estimated uncertainty of 0.5 arc sec. (radius, 90% confidence).

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
white_FC         132          281           147         18.9 +/- 0.1
white            871          1020          147         20.0 +/- 0.2
u_FC             289          539           246         18.7 +/- 0.1
v         796          1243           58         >18.7
b                545          565            19         18.9 +/- 0.4
uvw1             671          1292           78         >19.0
uvw2             596          1392           97         >19.2


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).








---------------------------------------------

Dr Samantha Oates

Leverhulme Early Career Fellow
Department of Physics
University of Warwick
Coventry
CV4, UK
Tel:  +44 (024) 765 23383
Email: s.oates@warwick.ac.uk<mailto:s.oates@warwick.ac.uk>
-----------------------------------------------