GCN Circular 18502
Subject
GRB 151027A: UVOT Observations
Event
Date
2015-10-28T01:04:14Z (11 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
B. G. Balzer (PSU), M. H. Siegel (PSU) and A. Maselli (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 151027A
96 s after the BAT trigger (Maselli et al., GCN Circ. 18478). We confirm
the source initially reported by Maselli et al. (GCN Circ. 18478) and
since observed by numerous ground-based observatories (Zheng and Filippenko,
GCN Circ. 18479; Elenin et al., GCN Circ. 18480; Perley and Cenko, GCN Circ.
18481; Xu et al., GCN Circ. 18485; Yano et al., GCN Circ. 18491; Wren et al.,
GCN Circ. 18495). We report a position of:
RA(J2000) = +18h 09m 57.26s
Dec(J2000) = +61d 21' 05.4"
The light curve shows complex behavior, with marginal evidence of brightening
after the initial finding chart, then fading with a decay slope of 0.6-0.8 over
the first orbit. The second orbit magnitudes are consistent with no fading
from those measured at the end of the first orbit while the third orbit
shows significant fading.
Preliminary detections 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) 95 245 147 14.52+-0.02
white 589 609 19 14.44+-0.04
white 762 782 19 14.71+-0.04
white 858 1008 147 14.81+-0.02
white 1161 1354 38 15.07+-0.04
white 1510 1529 19 15.23+-0.04
white 6449 6649 197 15.28+-0.01
white 23966 24662 677 17.14+-0.01
v 639 1579 116 15.12+-0.04
b 564 1505 97 15.37+-0.03
u 308 1479 323 14.00+-0.03
w1 688 1455 77 14.71+-0.05
m2 663 1598 88 14.98+-0.06
w2 615 1555 116 15.12+-0.05
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).