[vsnet-grb-info 28424] GRB 210725A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30527
SUBJECT: GRB 210725A: Swift/UVOT Upper Limits
DATE:    21/07/27 00:40:13 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at 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 210725A
114 s after the BAT trigger (Bernardini et al., GCN Circ. 30501).
No optical afterglow consistent with the XRT position (Perri et al. GCN Circ. 30517)
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)         114          264          147         >20.7
u (fc)             273          523          246         >20.2
white              114         1545          392         >21.0
v                  603         1595          117         >19.1
b                  529         1519           97         >20.4
u                  273         1495          343         >20.4
w1                 653         1470           97         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.047 in the direction of the burst
(Schlegel et al. 1998).