TITLE:   GCN CIRCULAR
NUMBER:  17942
SUBJECT: GRB 150616A: Swift/UVOT Upper Limits
DATE:    15/06/17 19:38:08 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150616A
579 s after the BAT trigger (Lien et al., GCN Circ. 17936).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 17937) is detected in the initial UVOT exposures.
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           579          729          147         >21.0
white              579         7913          616         >21.8
v                  736         2624          214         >19.6
b                  836         2878          365         >20.5
u                  810         2700          214         >20.5
w1                 786         2674          214         >20.2
m2                 760         2649          136         >19.9
w2                1016         2250          156         >20.1

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).