GCN Circular 41008
Subject
GRB 250706A: Swift/UVOT Upper Limits
Event
Date
2025-07-07T12:51:03Z (7 hours ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250706A
147 s after the BAT trigger (Moss et al., GCN Circ. 40988).
No optical afterglow consistent with the XRT position 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 147 397 246 >19.5
v 453 473 19 >16.8
b 403 423 19 >18.0
u 147 397 246 >19.5
w1 502 509 6 >18.2
m2 477 497 19 >17.9
w2 429 449 19 >19.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.093 in the direction of the burst
(Schlegel et al. 1998).