GCN Circular 4038
Subject
GRB050925: Swift UVOT upper limits
Event
Date
2005-09-26T17:04:31Z (20 years ago)
From
Simon Rosen at MSSL-UCL <srr@mssl.ucl.ac.uk>
S. Rosen (MSSL), S. T. Holland (GSFC/USRA), F. Marshall(GSFC),
P. Boyd (GSFC-UMBC), N. Gehrels (GSFC) on behalf of the Swift/UVOT team.
The Swift/UVOT began observing the field of the short-soft burst, GRB050925,
at 09:06:03 UT, 90s seconds after the BAT trigger (Holland et al., GCN 4034).
There has been no reported XRT detection of a fading afterglow and no
counterpart found in ground-based observations (GCN 4035 and 4036) so
no positional information other than the BAT location (revised position
from Markwardt et al., GCN 4037) is currently available.
Within the 1.5 arcmin BAT error circle (GCN 4037), no new optical/UV source
is detected and we derive the following 3 sigma upper limit magnitudes
on any optical/UV counterpart in the summed images in each UVOT filter
(from 6" radius apertures centred on the BAT location which is
representative of the local background).
Filter T_range(sec) Exp(sec) 3sig UL
V 90-50567 3885 20.2
B 3787-57196 4600 21.8
U 3682-56297 4654 21.2
UVW1 3578-52239 4080 21.4
UVM2 3473-51474 4541 21.8
UVW2 3892-62080 4356 21.8
Where T_range is the time post-trigger over which
the summed images were accumulated and Exp is the
total exposure time. The magnitudes upper limits
are not corrected for extinction which is high since
the BAT position is in the galactic plane.