GCN Circular 20959
Subject
GRB 170330A: Swift/UVOT Detection of a Fading Afterglow
Date
2017-03-31T15:32:32Z (7 years ago)
From
Sam Emery at MSSL-UCL <samuel.emery.15@ucl.ac.uk>
S.W.K. Emery (UCL-MSSL) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170330A
109 s after the BAT trigger (D'Avanzo et al., GCN Circ. 20944).
A fading source consistent with the XRT position
(Evans GCN Circ. 20945)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 18:53:19.36 = 283.33067 (deg.)
Dec (J2000) = -13:25:51.2 = -13.43090 (deg.)
with an estimated uncertainty of 0.46 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_FC 109 258 147 18.42 +/- 0.08
u_FC 266 516 246 >19.9
white 547 1368 225 19.94 +/- 0.21
v 596 1418 97 >18.4
b 522 1344 78 >19.3
u 266 1484 336 >20.0
w1 646 1467 97 >19.0
m2 621 1442 97 >18.9
w2 572 1393 78 >19.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.45 in the direction of the burst
(Schlegel et al. 1998).