GCN Circular 29933
Subject
GRB 210504A: Swift/UVOT Detection
Date
2021-05-04T20:42:29Z (4 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210504A 218 s after the BAT trigger
(Beardmore et al., GCN Circ. 29929). A fading source is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 14:49:34.03 = 222.39179 (deg.)
Dec (J2000) = -30:32:02.2 = -30.53395 (deg.)
with an estimated uncertainty of 0.6 arc sec. (radius, 90% confidence).
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 218 368 147 19.75 0.19
white 1168 1877 97 20.08 0.31
v 374 739 58 >18.26
b 473 837 58 >19.29
b 1144 1852 97 19.17 0.25
u 448 812 58 >18.89
uvw1 424 788 58 >18.49
uvm2 399 418 20 >17.24
uvw2 523 1040 59 >18.60