A Unified Model for GRB Prompt Emission from Optical to $\gamma$-Rays:   Exploring GRBs as Standard Candles
  The origin of prompt emission from gamma ray bursts remains to be an open question. Correlated prompt optical and gamma-ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the broadband GRB spectrum prompted the hypothesis of different emission mechanisms for the low- and high-energy radiations. We demonstrate that our multi-component model for GRB gamma-ray prompt emission provides an excellent fit to GRB 110205A from optical to gamma-ray energies. Our results show that the optical and highest gamma-ray emissions have the same spatial and spectral origin, which is different from the bulk of the X- and softest gamma-ray radiation. Finally, our accurate redshift estimate for GRB 110205A demonstrates promise for using GRBs as cosmological standard candles. 
S. Guiriec (1, 2, 3 and 4), C. Kouveliotou, D. H. Hartmann, J. Granot,   K. Asano, P. Meszaros, R. Gill, N. Gehrels and J. M...
astro-ph.HE astro-ph.CO