GCN Circular 29862
Subject
GRB 210420B: Swift/UVOT Detection
Event
Date
2021-04-21T14:42:18Z (5 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and M. J. Moss (GWU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210420B 147s after the BAT trigger
(Moss et al., GCN Circ. 29844 and updated in Lien et al., GCN Circ. 29854).
A fading source consistent with the optical counterpart reported by Lipunov et al. GCN Circ. 29845,
Oksanen GCN Circ. 29846, Hu et al. GCN Circ. 29847, Tianrui et al. GCN Circ. 29848, Leonini et al.
GCN Circ. 29851, de Ugarte Postigo et al. GCN Circ. 29852 and Watson et al. GCN Circ. 29858, is
detected in the initial UVOT exposures.
Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc.
1358, 373) for the first finding chart (_fc) exposure and other early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u_fc 147 391 240 16.2 �� 0.04
u 18793 19317 512 18.6 �� 0.1
v 447 467 20 16.7 �� 0.2
b 397 417 19 17.1 �� 0.1
w1 496 516 20 16.5 �� 0.2
m2 620 1121 39 17.2 �� 0.2
w2 1201 1371 39 17.6 �� 0.2
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of
E(B-V) = 0.022 in the direction of the burst (Schlegel et al. 1998).