GRB 990123: The case for saturated comptonization

We find that the optical magnitudes of GRB 990123 observed by the Robotic O ptical Transient Search Experiment move in tandem with the magnitudes extra polated from the simultaneous BATSE spectra, strongly suggesting that the o ptical, X-ray, and gamma-ray photons originate from a single source. We the n 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.