GCN Circular 11371
Subject
Swift/UVOT observations of GRB101023A
Event
Date
2010-10-24T13:44:00Z (15 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale, C. Saxton and S. Oates (UCL-MSSL)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB
101023A 93 s after the BAT trigger (Saxton et al, GCN Circ. 11363)
with a 100s finding chart in the white filter.
UVOT detected a fading optical source, with a position consistent
with the enhanced XRT position (Osborne et al, GCN Circ. 11365), in
the white filter exposures and, very marginally, in the first u
band exposure. We identify this object as the optical afterglow
of GRB101023A.
There is no detection of this source in other filters, either in
single or summed up exposures.
The position of this optical afterglow is
RA =21h 11m 51.26s (317.96360)
Dec = -65d 23m 15.7s (-65.38769) (J2000)
with an estimated uncertainty of 0.6 arcsec. This position is
consistent with the source identified by Gemini (Levan et al,
GCN Circ. 11366) and GROND Nardini et al., GCN 11369). We caution
that the photometry of this object is rather complicated by the
presence of a bright star 13rd magnitude star, which is located
about 15 arcseconds from the optical afterglow.
Preliminary magnitudes and 3-sigma upper limits using the UVOT
photometric system (Poole et al, 2008, MNRAS, 383, 627) for the
initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white (fc) 93 193 100 19.4 +/- 0.2
white 5895 10094 960 21.7 +/- 0.4 (2.8 sigma)
v 3524 15873 1082 >20.2
b 4344 4483 137 >20.2
u 4139 4339 200 20.5 +/- 0.6 (2 sigma)
u 21640 22548 882 >21.1
w1 3934 21633 1126 >21.1
m2 3728 16778 1082 >21.2
w2 10101 10653 544 >21.0
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).