GCN Circular 41015
Subject
GRB 250706B: Swift/UVOT Detection
Event
Date
2025-07-07T18:35:19Z (18 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 250706B 12.5 ks after the SVOM/ECLAIRs trigger (Palmerio et al., GCN Circ. 40989). A source consistent with the XRT position (Ferro et al., GCN Circ. 40996) and the optical transient (Zhu et al., GCN Circ. 40991; Palmerio et al., GCN Circ. 40992; Romanov, GCN Circ. 40995) is detected in the UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 02:44:53.43 = 41.23097 (deg.)
Dec (J2000) = -50:03:40.2 = -50.06116 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 12471 18805 2023 16.49+/-0.03
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.026 in the direction of the burst
(Schlegel et al. 1998).