GCN 43487: GRB 260120B: Swift/UVOT Detection

2026-01-21T14:04:46.458Z | rev 0 | event: GRB 260120B
A.A. Breeveld (UCL-MSSL) and M. Ferro (INAF-OAB) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 260120B 149 s after the BAT trigger (Ferro et al., GCN Circ. 43479).
A fading source consistent with the optical counterpart position given by Wu et al., (GCN Circ. 43483) and also the enhanced XRT position (Goad et al., GCN Circ. 43484) is detected in the initial UVOT exposures.

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

white              149          299          147         18.38 ± 0.06
white              588          776           35        >19.4
v                  637          657           19        >17.4
b                  563          755           39        >18.7
u                  307          557          246         18.80 ± 0.14
w1                 686          705           19        >17.4
m2                 661          681           19        >17.1
w2                 613          633           19        >17.5

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.063 in the direction of the burst (Schlegel et al. 1998).