[vsnet-grb-info 8226] GRB 090807: Liverpool Telescope observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9753
SUBJECT: GRB 090807: Liverpool Telescope observations
DATE:    09/08/08 11:31:45 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

C. Guidorzi (U. Ferrara), A. Gomboc (U. Ljubljana), R.J. Smith, C.G. 
Mundell,
I.A. Steele, A. Melandri, S. Kobayashi, C.J. Mottram, D.F. Bersier, Z. 
Cano (Liverpool JMU),
N.R. Tanvir, P. O'Brien (U. Leicester) report on behalf of a large 
collaboration:

On 2009 August 07 at 23:45:24 UT we observed the Swift GRB 090807
(Cannizzo et al., GCN Circ. 9746) with the 2-m Liverpool Telescope.

Observations started 8.75 hours after the BAT trigger time and were
performed using the r' and i' filters. We could not find any
uncatalogued object inside the UVOT-enhanced XRT error circle (Beardmore 
et al.
GCN Circ. 9748) down to the following limiting magnitudes:

Time Interval     Total Exp  Filter     Limit
(hours from GRB)   (s)                  (mag)
----------------------------------------------
8.75-9.27          6x300      R > 22.1
9.29-9.90          6x300      I > 22.0
----------------------------------------------

Magnitudes have been calibrated against the nearby USNOB-1 star
RA=18:15:00.349, Dec=+10:15:45.21, using R2=16.19, I=15.82.

We note the presence of an uncatalogued source lying outside the XRT error
circle at 4.2" from the XRT centroid, at RA=18:14:58.24, Dec=+10:15:58.4 
with
estimated magnitudes R=22.4 +/- 0.2, I=21.6 +/- 0.2:

http://www.fe.infn.it/u/guidorzi/090807_LT_ri.png

At the moment we cannot assess whether this source is fading.