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GCN Circular 23277

GRB 180924A: Swift/UVOT Upper Limits
2018-09-28T04:16:50Z (6 years ago)
Mike Siegel at PSU/Swift MOC <>
M. H. Siegel (PSU) and T. N. Ukwatta (LANL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180924A
83 s after the BAT trigger (Ukwatta et al., GCN Circ. 23261).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 23262)
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            83          233          147         >20.8
u_FC               241          491          246         >19.7
white               83          542          167         >20.9
v                  572          592           19         >17.1
b                  497          517           19         >18.4
u                  241          491          246         >19.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).
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