GCN Circular 36184
Subject
GRB 240418A: Swift/UVOT Upper Limits
Date
2024-04-19T16:06:19Z (14 days ago)
From
Sam Shilling at Lancaster University <shilling.sam@gmail.com>
Via
Web form
S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.), A. A. Breeveld (UCL-MSSL), N. P. M. Kuin (UCL-MSSL) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240418A
126 s after the BAT trigger (Siegel et al., GCN Circ. 36162).
No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 36166)
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 126 276 147 >20.6
u_FC 284 533 246 >19.4
white 126 5282 347 >21.1
v 4072 4272 197 >19.3
b 539 5093 216 >20.2
u 284 4888 442 >19.9
w1 4482 4682 197 >19.7
m2 4276 4476 197 >19.5
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.057 in the direction of the burst
(Schlegel et al. 1998).