TITLE:   GCN CIRCULAR
NUMBER:  13759
SUBJECT: GRB 120911A: optical upper limit ISON-NM
DATE:    12/09/13 07:13:47 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

L. Elenin (KIAM), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko 
(IKI) report on behalf of  larger GRB  follow-up collaboration:

We observed the field of  the Swift GRB 120911A (Cannizzo  et al., GCN 
13744) with 0.45-m telescope of ISON-NM observatory  starting on  Sep. 11 
(UT) 07:10:42, i.e ~130 s after burst trigger.  We took  several unfiltered 
images of 30 s and 60 s exposures.  Within enhanced XRT afterglow position 
(Beardmore et al., GCN 13748) we do not detect any new object.   A 
preliminary  photometry of single and co-added frames is based  on the 
USNO-B1.0 (R2)  nearby  stars is following:

  T0+,          Exposure,  OT,         UL (3 sigma)
  mid, d         (s)

 0.0017          30             n/d           18.4
 0.0028      5x30             n/d           19.1
 0.0175    60x30             n/d           20.2
 0.0590    30x120           n/d           20.6