[vsnet-grb-info 8474] GRB 091003: Swift/UVOT Detection of an Optical Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9990
SUBJECT: GRB 091003: Swift/UVOT Detection of an Optical Afterglow
DATE:    09/10/04 23:42:48 GMT
FROM:    Tyler Pritchard at PSU  <tapritchard at astro.psu.edu>

T. A. Pritchard (PSU) , E.A. Hoversten (PSU), and
R.L.C. Starling (U. Leicester) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of
GRB 091003 approximately 15.5 hours after the FERMI/GBM Trigger (Rau,
GCN Circ. 9983) A faint source is detected with 3.9-sigma confidence
in the summed UVOT observations at the Swift UVOT-enhanced XRT
position (R.L.C. Starling, et al. GCN Circ. 9988).

The observed magnitudes and upper limits using the UVOT photometric
system (Poole etal. 2008, MNRAS, 383, 627) for the initial exposures
are:

Filter   T_start(s)   T_stop(s)   Exp(s)          Mag
=======================================================================
w2        56820        64169    1150     21.08 ± 0.28 (3.9 sigma)
w1       103712       104474     750     20.70 ± 0.32 (3.4 sigma)
b         92252        92954     685     20.80 ± 0.26 (4.1 sigma)

m2	  98013        98715     691     > 21.63
v         86432        87195     741     > 20.27

The values quoted above 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).