GCN Circular 13808
Subject
GRB 120922A: Swift/UVOT Detection
Event
Date
2012-09-23T17:08:12Z (14 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (MSSL/UCL) and V.N. Yershov (MSSL/UCL) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of
GRB 120922A 127 s after the BAT trigger (Yershov et al., GCN
Circ. 13793). A source consistent with the XRT position (Evans et al.
GCN Circ. 13800), and the initial optical detection by GROND (Knust
et al., GCN Circ. 13795) is detected in the initial UVOT exposures
(Yershov et al. GCN Circ. 13803).
The uvot observations show a slow initial rise in brightness peaking
around 900s after the trigger. The burst is only detected in the v,b and
white filters which is probably due to the high galactic reddening.
Preliminary detections and 3-sigma upper limits using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358,
373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 126 276 147 >20.67
white 865 1014 147 19.34 +/- 0.14
v 615 1239 78 17.94 +/- 0.22
b 541 733 78 >19.17
b 1145 2030 119 19.62 +/- 0.36
u 285 534 250 >19.98
u 688 1139 40 >18.82
w1 664 16852 1434 >20.95
m2 639 11081 1232 >20.96
w2 590 12900 1424 >21.20
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.15 in the direction of the burst
(Schlegel et al. 1998).