GCN Circular 40010
Subject
GRB 250329A: Swift/UVOT Upper Limit
Date
2025-04-02T15:12:53Z (a month ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M.H. Siegel (PSU) and R. Caputo (GSFC) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250329A 6.8ks after the SVOM trigger sb25032901 (Wang et al., GCN Circ. 39916). We do not detect an afterglow at the position of the XRT counterpart (Dichiara et al., GCN Circ. 39924) or optical-infrared counterparts (Watson et al., GCN Circ. 39915; Want et al., GCN Circ. 39917; Ghosh et al., GCN Circ. 39922). The lack of detection in the u-band for this bright burst would be consistent with the redshift of z=2.9 reported by Schneider et al. (GCN Circ. 39918).
Preliminary detections and 3-sigma upper limits for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag(AB)
u 6812 13135 1551 >20.95
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.021 in the direction of the burst (Schlegel et al. 1998).