GCN Circular 23205
Subject
GRB 180904A: Swift/UVOT Upper Limits
Event
Date
2018-09-05T15:58:34Z (8 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180904A
131 s after the BAT trigger (D'Ai et al., GCN Circ. 23194).
No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 23196)
is detected in the initial UVOT exposures, consistent with the non-detections
of Malesani et al. (GCN Circ. 23195), Izzy et al. (GCN Circ 23197),
Moskvitin et al. (GCN Circ. 23198) and Guidorzi et al. (GCN Circ. 23199).
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 131 281 147 >21.1
u_FC 289 539 246 >20.1
white 131 589 167 >21.1
v 620 640 19 >20.1
b 545 565 19 >19.4
u 289 539 246 >20.1
w1 670 690 19 >18.1
w2 595 615 19 >18.6
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).