[vsnet-grb-info 1999] Swift/UVOT photometry of GRB050820

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3838
SUBJECT: Swift/UVOT photometry of GRB050820
DATE:    05/08/20 21:04:12 GMT
FROM:    Margaret Chester at PSU  <chester at astro.psu.edu>

M. Chester (PSU), M. Page (UCL-MSSL), P. Roming (PSU),
F. Marshall (GSFC), P. Boyd (GSFC), L. Angelini (GSFC-JHU),
J. Greiner (MPE), N. Gehrels (GSFC), on behalf of the Swift UVOT team.


Swift/UVOT began observing GRB050820 at 06:36:13 UT.
The initial 100-second finding chart exposure in V was cut short
due to entry into the SAA; it was repeated on the second orbit.


The afterglow is detected in the V, B, U, and one UV band.
Similar to the ground-based observations (GCN #3829),
UVOT sees a rising, then falling, light curve in V.
Analysis in the other bands is continuing.


V-band Observations:
Time-Since-Trigger       V
   80 s               18.2 ± 0.3
 4635 s               17.6 ± 0.2
12238 s               18.2 ± 0.2


Other:
Time-Since-Trigger    Mag          Filter
 5647 s                18.3 ± 0.2       U
10423 s                19.0 ± 0.1       B
 4741 s                20.4 ± 0.2       UVW1
11331 s               >21.0             UVW2


The magnitudes have not been corrected for extinction.
Upper limits are given at the 5-sigma level.