GCN Circular 3878
Subject
GRB050824: Swift/UVOT detection of fading afterglow
Event
Date
2005-08-25T17:41:46Z (20 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
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 1.8 109 20.02+/-0.39
B 5.1 305 20.88+/-0.36
U 3.6 217 19.55+/-0.32
W1 9.5 205 19.85+/-0.33
M2 11.7 121 19.34+/-0.36
W2 12.3 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. These magnitudes
are based on preliminary zero-points, measured in orbit, and will require
refinement with further calibration.