[vsnet-grb-info 8643] GRB 091109B: Optical limits from Watcher

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10150
SUBJECT: GRB 091109B: Optical limits from Watcher
DATE:    09/11/09 23:47:07 GMT
FROM:    Petr Kubanek at AIO  <petr at lascaux.asu.cas.cz>

M. JelĂ­nek (IAA-CSIC), A. de Ugarte Postigo (INAF-OAB), R. Felletti, L.
Hanlon (UCD Dublin), H. Van Heerden (UOVS, Bloemfontein), P. KubĂĄnek
(IPL UV, IAA-CSIC) reports on behalf of a large collaboration:

Watcher telescope, located at Boyden Observatory, South Africa,
observed autonomously GRB 091109B (S. R. Oates et al., GCN 10148). We
obtained a set of 5s exposures in clear filter, starting 78s after the
GRB (65s after the notice). We see no new sources in the XRT error box
down to the single-image limiting magnitude of 16.5. Coaddition of
first 120s (mean exposure time 153s after the GRB) of imaging data
improves this limit to ~17.7 calibrated against field USNO-A2.0 R-band
stars. Those results are consistent with ROTSE-III non-detection
(Schaefer et al. GCN 10149).

We note that there is a R~15.3 galaxy 8" North-West of the XRT position,
posibly the host of this short GRB.

Further observations are ongoing. This message can be quoted.