GRB 990123:: The case for saturated comptonization

We find that the optical magnitudes of GRB 990123 observed by the Robotic Optical Transient Search Experiment move in tandem with the magnitudes extrapolated from the simultaneous BATSE spectra, strongly suggesting that the optical, X-ray, and gamma-ray photons originate from a single source. We then show that the broadband optical-gamma-ray spectra can be naturally fit by the saturated Compton model. We also derive the parameters of the Compton emitting shell from first principles.