TITLE:   GCN CIRCULAR
NUMBER:  9200
SUBJECT: GRB 090423: Faulkes Telescope South observations
DATE:    09/04/23 09:42:02 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm@astro.livjm.ac.uk>

A. Melandri (Liverpool JMU), C. Guidorzi (U. Ferrara), C.G. Mundell,
D. Bersier (Liverpool JMU), P. O'Brien, N. Tanvir (U. Leicester) on
behalf of a large collaboration report:


On 2009 April 23 at 07:57:07 UT we observed the Swift-BAT GRB 090423
(Krimm et al., GCN Circ. 9198) with the 2-m Faulkes Telescope South.

Observations started 108 seconds after the BAT trigger time and were
performed using the B, R and i' filters. We could not find any
uncatalogued object inside the XRT error circle down to the following
limiting magnitudes:

For single frames:

Mid Time   Exposure  Filter   Limit
  (min)       (s)              (mag)
-------------------------------------
16.05         60      i'      > 18.0
21.30        120      r'      > 20.0
24.29        120      i'      > 19.0
-------------------------------------

For coadded frames:

Time Range   Exposure  Filter  Limit
  (min)         (s)             (mag)
-------------------------------------
13.58-53.82    660      r'     > 20.8
15.55-45.95    420      i'     > 20.5
-------------------------------------

Calibration was performed using few SDSS nearby stars on both filters.