We present an analysis of time-resolved optical emissions observed from the gamma-ray burst ( catalog 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 ( catalog 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 sec .
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 .