TITLE:   GCN CIRCULAR
NUMBER:  32785
SUBJECT: GRB 221016A: Swift/UVOT Detection
DATE:    22/10/17 20:13:01 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 221016A
97 s after the BAT trigger (Page et al., GCN Circ. 32774).
A source consistent with the enhanced XRT position (Goad et al. GCN Circ. 32776)
is detected in the initial UVOT exposures.

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               97          247          147         20.20 +/- 0.23
b                 3736         3861          123        >19.8
u                  309          349           39        >18.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.026 in the direction of the burst
(Schlegel et al. 1998).