[vsnet-grb-info 8679] GRB 091117A: Swift/UVOT followup observations
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Fri Nov 20 20:32:23 JST 2009
TITLE: GCN CIRCULAR
NUMBER: 10184
SUBJECT: GRB 091117A: Swift/UVOT followup observations
DATE: 09/11/20 11:32:17 GMT
FROM: Alice Breeveld at MSSL-UCL <aab at mssl.ucl.ac.uk>
A. Breeveld (MSSL/UCL), M. De Pasquale (MSSL/UCL) and J. R. Cummings
(GSFC/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 091117A
96767s (~27 hours) after the BAT trigger (Cummings et al., GCN Circ.
10171). The galaxy described by Berger and Mulchaey (GCN Circ. 10174)
as being a possible host, is clearly seen as an extended object in the
UVOT data. There is no evidence of a fading source at either of the
two XRT source positions (D'Elia et al., GCN Circ. 10177) when
compared with data taken ~47 hours after the burst. In the case of
source 1, which is coincident with the spiral galaxy, we checked for
fading using an aperture of 2" at the refined XRT position as well as
using an aperture of 8" to contain the whole galaxy.
Magnitudes measured with a non-standard 8" aperture to include the
whole galaxy, using the UVOT photometric system (Poole et al. 2008,
MNRAS, 383, 627), for the initial summed exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 97197 113850 875 17.56 ± 0.01
v 109296 109642 340 17.05 ± 0.06
u 96767 119064 2614 17.60 ± 0.02
Upper limits (3 sigma) obtained at the position of source 2 (D'Elia et
al., GCN Circ. 10181) are as follows:
white 97197 113850 875 21.89 (UL)
v 109296 109642 340 19.72 (UL)
u 96767 119064 2614 21.52 (UL)
None of the values quoted above are 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).
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