GCN Circular 29247
Subject
GRB 210104A: Swift/UVOT Detection
Event
Date
2021-01-04T22:21:25Z (5 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210104A 71 s after the BAT trigger
(Troja et al., GCN Circ. 29233).
A fading source is detected in all UVOT filters in the initial exposures, at the position given in
Troja et al., (GCN Circ. 29233), and also seen by others (Xin et al., GCN Circ. 29235; Hosokawa et
al., GCN Circ. 29237; Kim et al., GCN Circ. 29238; Lipunov et al., GCN Circ. 29239 and Horiuchi et
al., GCN Circ. 29241).
Preliminary detections 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_FC 71 221 147 14.61 �� 0.02
white 562 582 20 16.23 �� 0.05
white 1512 1706 39 17.02 �� 0.05
b 538 558 20 16.59 �� 0.10
u_FC 283 533 246 15.28 �� 0.03
v 613 632 20 16.36 �� 0.16
uvw1 662 682 20 16.12 �� 0.16
uvm2 637 657 20 16.58 �� 0.25
uvw2 588 608 20 17.09 �� 0.26
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of
E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).