Correlated optical and gamma emissions from GRB 081126
  We present an analysis of time-resolved optical emissions observed from the
gamma-ray burst GRB 081126 during the prompt phase. The analysis employed
time-resolved photometry using optical data obtained by the TAROT telescope,
using BAT data from the Swift spacecraft, and time-resolved spectroscopy at
high energies from the GBM instrument onboard the Fermi spacecraft. The optical
emission of GRB 081126 is found to be compatible with the second gamma emission
pulse shifted by a positive time lag of 8.4 $\pm$ 3.9 s. This is the first
well-resolved observation of a time lag between optical and gamma emissions
during a gamma-ray burst. Our observations could potentially provide new
constraints on the fireball model for gamma-ray burst early emissions.
Furthermore, observations of time lags between optical and gamma ray photons
provides an exciting opportunity to constrain quantum gravity theories.
