GCN Circular 41265
Subject
GRB 250805A: Swift/UVOT Upper Limits
Event
Date
2025-08-07T12:47:42Z (11 days ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250805A
3536 s after the BAT trigger (Ambrosi et al., GCN Circ. 41233).
No optical afterglow consistent with the XRT position (Beardmore et al.,
GCN Circ. 41238) or optical afterglow (Izzo et al., GCN Circ. 41241; Li et
al., GCN Circ. 41241) 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 3536 3686 147 >21.3
white 3536 4306 344 >21.7
b 3902 4101 197 >20.9
u 3696 3895 197 >20.6
w2 4312 4460 146 >20.7
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.092 in the direction of the burst
(Schlegel et al. 1998).