GCN Circular 34486
Subject
GRB 230818A: Swift/UVOT Detection
Date
2023-08-19T07:46:57Z (a year ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and A. Tohuvavohu (U. Toronto)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230818A
144 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 34479).
A source consistent with the optical position (Lipunov et al., GCN
Circ. 34476) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 19:03:33.13 = 285.88806 (deg.)
Dec (J2000) = +40:53:49.0 = 40.89695 (deg.)
with an estimated uncertainty of 0.48 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 144 294 147 19.09 +/- 0.07
v 379 572 39 18.40 +/- 0.30
b 477 1513 117 19.68 +/- 0.20
u 452 1487 117 >19.5
w1 428 1463 97 >20.2
w2 1026 4987 255 >20.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.101 in the direction of the burst
(Schlegel et al. 1998).