GCN Circular 18161
Subject
GRB 150818A: Swift/UVOT Detection
Event
Date
2015-08-18T20:39:33Z (11 years ago)
From
Marissa McCaule at PSU <marissamc@swift.psu.edu>
L. M. McCauley (PSU), L. M. Z. Hagen (PSU), and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150818A
94 s after the BAT trigger (D'Elia et al., GCN Circ. 18152).
A source consistent with the XRT position (Beardmore et al. GCN Circ. 18159)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 15:21:25.43 = 230.35594 (deg.)
Dec (J2000) = +68:20:33.0 = 68.34251 (deg.)
with an estimated uncertainty of 0.66 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 94 121 27 19.39+-0.25
white 3414 4790 344 19.92+-0.17
white 10222 10826 590 19.68+-0.07
v 3572 5201 393 >19.36
b 4385 4585 196 >20.16
b 5821 10217 927 20.56+-0.33
u 4180 4379 196 >19.66
u 5616 5816 196 19.63+-0.25
uvw1 3976 4175 195 18.78+-0.20
uvw1 5411 5611 196 18.95+-0.20
uvm2 3776 3976 192 18.81+-0.23
uvm2 5206 5406 196 18.89+-0.24
uvw2 4796 4996 196 18.90+-0.19
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).