GCN Circular 23152
Subject
GRB 180818B: Swift/UVOT Upper Limits
Date
2018-08-18T18:08:33Z (6 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) and F. E. Marshall (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180818B
212 s after the BAT trigger (Marshall et al., GCN Circ. 23149).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 23151)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 212 362 147 >19.9
white 212 11082 1482 >21.1
v 369 12690 1148 >19.8
b 467 6919 471 >19.9
u 442 6714 469 >19.6
w1 418 6509 468 >19.9
m2 393 6304 471 >20.5
w2 517 11988 1160 >20.3
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.09 in the direction of the burst
(Schlegel et al. 1998).