GCN Circular 30526
Subject
GRB 210725B: Swift/UVOT Upper Limits
Date
2021-07-27T00:38:22Z (3 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M. H. Siegel (PSU) and M. G. Bernardini (INAF-OAB)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210725B
92 s after the BAT trigger (Bernardini et al., GCN Circ. 30508).
No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 30510)
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
u (fc) 92 341 246 >20.5
b 347 439 91 >20.0
u 92 341 246 >20.5
w2 3722 3905 180 >19.4
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.023 in the direction of the burst
(Schlegel et al. 1998).