[vsnet-grb-info 2041] GRB050824: CORRECTION to UVOT observing times

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3880
SUBJECT: GRB050824: CORRECTION to UVOT observing times
DATE:    05/08/25 19:00:58 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps at mssl.ucl.ac.uk>

P. Schady (MSSL/PSU), R. Fink (GSFC), M. Ivanushkina (PSU), S. Holland 
(GSFC/USRA), K. McGowen (MSSL), N. Gehrels (GSFC) on behalf of the Swift 
UVOT team

CORRECTION: The mid time and exposure durations previously reported for 
observations made by Swift/UVOT of GRB050824 are incorrect (Schady et al. 
GCN 3878). The correct times are given below.

The Swift Ultra-Violet/Optical Telescope (UVOT) observations began at
00:53:49 UT, 1.8 hrs after the BAT trigger. UVOT detects a fading source 
at a
position consistent with that reported by Gorosabel et al. (GCN 3865) in 5
of its 6 filters. The magnitudes or 3-sigma upper limit in the first
exposure taken in each filter are as follows:

Filter  Mid Time (hrs)  Exp (s)  Mag/3-sig UL
V       1.8             900     20.02+/-0.39
B       5.1             900     20.88+/-0.36
U       3.6             545     19.55+/-0.32
W1      3.4             900     19.85+/-0.33
M2      2.1             532     19.34+/-0.36
W2      7.8             1457    > 20.79

The afterglow has faded below 2-sigma above background 11hrs after the
burst trigger in all filters apart from the V and U, where it is still
detected at the 2.3-sigma and >3-sigma level, respectively.

The magnitudes have not been corrected for extinction. The reddening in
this direction is E_{B-V} = 0.04mag. These magnitudes are based on
preliminary zero-points, measured in orbit, and will require refinement
with further calibration.