TITLE:   GCN CIRCULAR
NUMBER:  18322
SUBJECT: GRB 150915A: Swift UVOT upper limits
DATE:    15/09/16 17:53:39 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

A. A. Breeveld (UCL-MSSL) and V. D'Elia (ASDC) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150915A
295s after the BAT trigger (D'Elia et al., GCN Circ. 18315).
No optical afterglow consistent with the XRT position (D���Elia et al.,
GGN Circ. 18315) or the GROND position (Yates et al., GCN Circ. 18317)
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               295          545          246         >20.0
white              576          769           39         >19.9
v                  625          818           39         >18.2
b                  550          745           39         >19.2
u                  295         4267          434         >20.0

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.10 in the direction of the
burst (Schlegel et al. 1998).