GCN Circular 12236
Subject
Swift/UVOT observations of GRB110801A
Date
2011-08-02T12:52:23Z (13 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL-UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 110801A
109 s after the BAT trigger (De Pasquale et al., GCN Circ. 12228).
A source consistent with the XRT position (Evans et al., GCN Circ. 12232)
is detected in the initial and summed UVOT exposures, except in um2
filter and a detection in uw2, at 2 sigma confidence level. Since
the redshift of this event is 1.86 (Cabrera Lavers, GCN Circ. 12234),
we think the weak detection in uw2 is due to flux in the reddest part
of this filter.
The refined UVOT position is:
RA (J2000) = 05:57:44.87 = 89.43695 (deg.)
Dec (J2000) = +80:57:21.1 = 80.95592 (deg.)
with an estimated uncertainty of 0.51 arc sec. (radius, 90% confidence).
The afterglow shows a quick rise from the first exposure up to ~300s.
Preliminary detections and 3-sigma upper limits using the UVOT photometric
system (Poole et al. 2008, MNRAS, 383, 627) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white (fc) 109 259 147 18.06 � 0.07
white 109 6337 727 17.23 � 0.05
v 598 6747 451 17.07 � 0.06
b 523 6132 432 17.47 � 0.05
u (fc) 267 517 246 15.89 � 0.05
u 267 5927 488 15.68 � 0.04
w1 647 5722 255 17.92 � 0.11
m2 622 6904 404 >20.2
w2 573 6543 452 20.48 � 0.41
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.08 in the direction of the burst
(Schlegel et al. 1998).