[vsnet-grb-info 2189] GRB050922B: Swift UVOT early upper limits.

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4028
SUBJECT: GRB050922B: Swift UVOT early upper limits.
DATE:    05/09/23 15:09:06 GMT
FROM:    Massimiliano de Pasquale at MSSL-UCL  <mdp at mssl.ucl.ac.uk>

  M. De Pasquale (MSSL), J. Norris (GSFC),
T. Kennedy (GSFC), K. Mason (PPARC), N. Gehrels
(GSFC) on behalf of the Swift/UVOT team

The Swift/UVOT began observing the field of
GRB050922B at 15:07:42 UT, 342 seconds after the
BAT trigger (Hullinger et al., GCN 4019).
There is no detection of an optical counterpart
in the first 100 sec exposure finding chart
down to a 3 sigma upper limit of V=18.7.

  There is also no optical/UV counterpart
detected in the summed images from all filters,
down to the following 3 sigma magnitude upper
limits:

  Filter  T_range(sec)  Exp(sec)  3sig UL

    V      342-5997      1158     20.1
    B      489-1720       258     20.2
    U      474-11434      720     20.5
    UVW1   580-7616       873     20.3
    UVM2   446-6904      1068     20.6
    UVW2   503-1826       258     20.1

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.

  These magnitudes are based on preliminary zero-
points, measured in orbit, and will require
refinements with further calibrations.