TITLE: GCN CIRCULAR NUMBER: 39861 SUBJECT: GRB 250322A: Swift/UVOT Upper Limits DATE: 25/03/24 12:52:39 GMT FROM: Sam Shilling at Lancaster University shilling.sam@gmail.com
S. P. R. Shilling (Lancaster U.) and R. Gupta (NASA/GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250322A 77 s after the BAT trigger (Gupta et al., GCN Circ. 39835). No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 39841) 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
white_FC 77 226 147 >20.5 u_FC 291 541 246 >19.8 white 77 1711 411 >20.9 v 620 1760 136 >18.9 b 546 1686 117 >19.7 u 291 1661 343 >20.0 w1 669 1807 134 >19.2 m2 644 1785 136 >19.0 w2 596 1736 136 >19.2
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.153 in the direction of the burst (Schlegel et al. 1998).
View this GCN Circular online at https://gcn.nasa.gov/circulars/39861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...