GCN Circular 40691
Subject
GRB 250610B: Swift/UVOT Detection
Date
2025-06-11T15:39:28Z (4 days ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
Via
email
A.A. Breeveld (UCL-MSSL) and M.A. Williams (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250610B
2 ks after the SVOM trigger (Saccardi et al., GCN Circ. 40671).
The optical source at the position of XRT source 1 (Evans et al., GCN Circ. 40679) seen by Schneider et al., (GCN Circ. 40676), Gompertz et al., (GCN Circ. 40677), Li et al., (GCN Circ. 40678), Bochenek et al., (GCN Circ. 40684) and Qiu et al. (GCN Circ. 40685) was also detected in the UVOT U-band filter and shows signs of fading.
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 2939 4660 1694 20.20 ± 0.15
u 8634 8923 285 20.50 ± 0.36
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.0104 in the direction of the burst (Schlegel et al. 1998).