GCN Circular 3549

P. Brown (PSU), A. Retter (PSU), P. Schady (MSSL), P. Boyd (GSFC),
S. T. Holland (GSFC/USRA), P. Roming (PSU), C. Gronwall (PSU),
N. Cucchiara (PSU), K. Mason (MSSL), N. Gehrels (GSFC),
on behalf of the Swift UVOT team:

The second V-filter magnitude (V=21.8 at T_start=32997) reported in
GCN 3516
Not found
 
 
 for the fading afterglow of GRB050603 is incorrect.  An error
in the on-board shift-and-add code resulted in an unusually large
amount of missing data for this exposure that was not correctly
recorded in the exposure information.  The real exposure time for the
second exposure was adjusted to 101 s to match the actual data
contained in the image.  The corrected magnitude is 18.7, meaning the
afterglow only faded by 0.5 magnitudes between the two observations
reported in GCN 3516
Not found
 
 
.

In addition, we report the afterglow magnitude in later exposures.
An error-weighted powerlaw fit gives a decay index of 1.97 +/- 0.22.
The corrected and new afterglow magnitudes from UVOT are as follows:

Time (h)      Mag        Filter  Duration (s)
9.5       18.2 +/- 0.1     V       1298
10.9      18.7 +/- 0.4     V       101
12.7      19.5 +/- 0.2     V       1772
14.4      19.3 +/- 0.2     V       2104
15.9      19.0 +/- 0.2     V       1200
17.8      19.7 +/- 0.3     V       1205
20.8      20.1 +/- 0.4     V       1948
36.1      21.1 +/- 0.4     V       10,458 (9 exposures coadded)

Time (h) is the midpoint of the exposure given in hours after the
burst trigger.  The reported errors do not include a +/- 0.09 error in
the preliminary inflight zero point calibration.