TITLE:   GCN CIRCULAR
NUMBER:  40747
SUBJECT: GRB 250615A: Swift/UVOT Upper Limits
DATE:    25/06/16 11:38:35 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

N.P.M.Kuin (UCL/MSSL) and S. Dichiara (PSU) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250615A
152 s after the BAT trigger (Dichiara et al., GCN Circ. 40736).
No optical afterglow consistent with the enhanced XRT position (Goad et
al., GCN Circ. 40739) 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

u_FC               152          402          246         >19.8
white              432         1722          284         >21.0
v                  483         1772          156         >19.5
b                  408         1697          136         >20.7
u                  152         1672          363         >20.0
w1                 532         1821          136         >19.5
w2                 804         1747           78         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.165 in the direction of the burst
(Schlegel et al. 1998).