GCN Circular 40982
Subject
GRB 250704B: Swift/UVOT Upper Limits
Event
Date
2025-07-05T18:41:26Z (16 hours ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250704B 2.0 ks after the SVOM/GRM trigger (Wang et al., GCN Circ. 40940). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40951) or the reported optical counterparts (Malesani et al., GCN Circ. 40945; Gillanders et al., GCN Circ. 40958; Xin et al., GCN Circ. 40960) 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) are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 2024 7891 1944 20.02+/-0.12
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.115 in the direction of the burst
(Schlegel et al. 1998).