[vsnet-grb-info 28583] GRB 210820A: Swift/UVOT Detection
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Mon Aug 23 04:55:38 JST 2021
TITLE: GCN CIRCULAR
NUMBER: 30686
SUBJECT: GRB 210820A: Swift/UVOT Detection
DATE: 21/08/22 19:54:45 GMT
FROM: Sam LaPorte at PSU <sjl5346 at psu.edu>
GRB 210820A: Swift/UVOT Detection
S. J. LaPorte (PSU) 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 210820A
131 s after the BAT trigger (Beardmore et al., GCN Circ. 30664).
A source consistent with the XRT position
(Beardmore et al., GCN Circ. 30664)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 01:22:33.48 = 20.63952 (deg.)
Dec (J2000) = +04:36:28.3 = 4.60786 (deg.)
with an estimated uncertainty of 0.45 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
v 437 1684 156 18.86 +/- 0.24
b 387 555 39 18.57 +/- 0.19
u 131 381 246 17.60 +/- 0.06
w1 784 1733 58 >19.0
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.030 in the direction of the burst
(Schlegel et al. 1998).
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