GCN Circular 12742

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (OHP-CNRS), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 111228A detected by SWIFT
(trigger 510649) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The trigger occured during daytime over Calern.
The observations started 289 min after the GRB trigger
The elevation of the field increased from 7 degrees
above horizon and weather conditions were good.

We detect the candidate couterpart mentioned by Ukwatta et al.
(GCNC 12737) and confirmed by Xin et al. (GCNC 12738) using
a co-addition of 10 images of 3mins. Surprisingly, the OT
is bright R~18 (Tstart=289 min, Tend=336 min) corresponding
to an optical decay alpha~0.3 taken TNT and TAROT data.
We suspect a rebrightening occured during the first minutes
after the trigger.

Netherveless, the low elevation and the 3 arcsec/pix
sampling of TAROT does not allow to discriminate
the OT from the star NOMAD1 1082-0210617 (RA=150.0646861
DEC=+18.2997694 R=19.9). Now TAROT continues observations
in better airmass conditions but other observations are
encouraged.

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