[vsnet-grb-info 7771] GRB 090423: optical limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9323
SUBJECT: GRB 090423: optical limit
DATE:    09/05/05 00:21:38 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

V. Rumyantsev, E. Pavlenko, O. Antoniuk (CrAO), A. Pozanenko (IKI) report on 
behalf of  larger GRB follow-up collaboration:

We observed the error box of  Swift GRB 090423 (Krimm et al. GCN 9198)  on 
Apr. 23 between (UT)  090423 23:34:46 -- 090424 01:13:20 in R -filter with 
Shajn telescope of CrAO.  The observation was planning and performed before 
the redshift z ~ 8 of GRB 090423 was confirmed  (Cucchiara et al. GCN 9213; 
Olivares et al. GCN  9215; Thoene  et al.  GCN 9216; Tanvir et al.  GCN 
9219). Indeed we do not detect optical afterglow at the place of IR 
afterglow detection (Tanvir et al.  GCN 9202; Levan et al.  GCN 9206; 
Cucchiara  et al.  GCN  9209).  Limiting magnitude of the combined image is 
following :

T0+     Filter, Exposure, mag.,     err.
(d)                  (s)

0.6877  R       93x60    >24.0 (3 sigma)

The combined R-image  can be found at 
http://grb.rssi.ru/GRB090423/GRB090423_ZTSh_a.gif