TITLE:   GCN CIRCULAR
NUMBER:  13855
SUBJECT: GRB 121011A: optical observations
DATE:    12/10/11 22:32:41 GMT
FROM:    Alexei Pozanenko at IKI  <alex@grb.rssi.ru>

A. Volnova (SAO MSI, IKI), A. Matkin (UAFO, ISON), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of the Swift GRB 121011A (Racusin et al., GCN 13845) with VT-50 (0.5-m) telescope of UAFO/ISON-Ussuriysk observatory starting on Oct. 11 (UT) 11:21:29, i.e. 6 minutes after burst trigger. We took several unfiltered images of 30 s exposures ending observations on (UT) 12:17:00. In initial frames we clearly detect afterglow (Racusin et al., GCN 13845). Preliminary photometry of some early images is based on USNO-B1.0 stars (R2):

T_start T0+, Filter, exposure, OT 
(UT) mid (d) (s) 

11:21:29 0.00433 none 30 16.70 +/- 0.08
11:27:04 0.00821 none 30 16.64 +/- 0.07
11:33:14 0.01249 none 30 16.80 +/- 0.10
11:38:12 0.01594 none 30 17.30 +/- 0.10