TITLE:   GCN CIRCULAR
NUMBER:  12446
SUBJECT: GRB 111016A: Swift/UVOT Detection of a Source
DATE:    11/10/17 18:18:13 GMT
FROM:    Tyler Pritchard at PSU  <tapritchard@astro.psu.edu>

T. A. Pritchard (PSU) and V. Mangano (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 111016A
188 s after the BAT trigger (Mangano et al., GCN Circ. 12439).
No optical afterglow consistent with the Enhanced Swift-XRT position
(Evans et al., GCN Circ 12441) is detected in the initial UVOT exposures,
however a marginal source is detected in followup observations in the
UVOT white filter.  This position is consistent with the source observed by
Cenko et all (GCN Circ 12444).  Preliminary 3-sigma upper limits and
magnitudes using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent exposures are:

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

white_FC           188          337          147 >20.3
u_FC               345          595          246 >19.3
white              188        23781         1926 >21.5
white            27360        45216         4662         21.56
v                 4468        16602         1278 >20.5
b                 5288        23264         1967 >21.6
u                  345        22351         1328 >20.4
w1                 724        18207         1095 >20.5
m2                 700        17507         1298 >20.8
w2                 651        12429         1135 >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).