TITLE:   GCN CIRCULAR
NUMBER:  17521
SUBJECT: GRB 150301A: Swift/UVOT Upper Limits
DATE:    15/03/02 00:59:47 GMT
FROM:    Lea Hagen at PSU  <lea.zernow.hagen@gmail.com>

L. M. Z. Hagen (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 150301A
66 s after the BAT trigger (Lien et al., GCN Circ. 17510).
No optical afterglow consistent with the XRT position (Lien et al.
GCN Circ. 17510) or GROND candidates (Tanga et al. GCN Circ. 17513)
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
exposures are:

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

white               66         4931          306        >21.08
v                 5143         5343          196        >19.40
b                 4526        10879          750        >21.16
u                 4321         5926          362        >20.08
uvw1              5553         5752          196        >19.61
uvm2              5347         5547          196        >19.40
uvw2              4937         5137          196        >19.82

The magnitudes in the table are not corrected for the substantial Galactic
extinction due to the reddening of E(B-V) = 3.84 in the direction of the
burst (Schlegel et al. 1998).  We note that the photometry is likely
affected by a nearby bright foreground star.