GCN Circular 38866
Subject
GRB 250108A: Swift/UVOT Upper Limits
Date
2025-01-09T10:33:26Z (9 days ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
Via
email
A. A. Breeveld (UCL-MSSL) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of SVOM/ECLAIRs-detected burst GRB 250108A 102468 s after the SVOM trigger (Zheng et al., GCN Circ. 38845).
No optical afterglow consistent with either the Swift-XRT proposed X-ray counterpart (Ambrosi et al., GCN Circ. 38853) or the VT optical afterglow candidate (Qiu et al., GCN Circ. 38852), 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 initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
w1 102468 109462 2632 >20.9
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.012 in the direction of the burst (Schlegel et al. 1998).