TITLE:   GCN CIRCULAR
NUMBER:  26024
SUBJECT: GRB 191016A: Swift/UVOT Detection
DATE:    19/10/17 23:13:53 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191016A
45 ks after the BAT trigger (Gropp et al., GCN Circ. 26008).  A 
source is detected consistent with the XRT position and the optical source reported
by Watson et al. (GCN Circ. 26010, 26015), Zheng and Filippenko (GCN Circ. 26011),
Hu et al. (GCN Circ. 26017), Kim et al. (GCN Circ. 26018) and Toma et al.
(GCN Circ. 26019).

The preliminary UVOT position is:
    RA  (J2000) =  02:01:04.68 =  30.26948 (deg.)
    Dec (J2000) = +24:30:35.7  =  24.50990 (deg.)
with an estimated uncertainty of 0.5 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limit 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            45023        46878         1822        21.09+/-0.17
white            50812        52638         1794        21.21+/-0.19
white            56420        56938          506        >21.23

The magnitudes in the table are not corrected for the Galactic extinction due
to the reddening of E(B-V) = 0.09 in the direction of the burst (Schlegel et al. 1998).