GRB990123: The Case for Saturated Comptonization

TL;DR

This paper presents evidence supporting the saturated Comptonization model for GRB990123, showing a single leptonic source explains the broadband emission from optical to gamma-rays and aligns with observed spectral evolution.

Contribution

It demonstrates that the entire continuum from optical to gamma-rays can originate from a single leptonic source, supporting the saturated Comptonization model for GRB spectra.

Findings

Correlation between gamma-ray spectral shape and optical emission.

Optical lag due to high initial Thomson depth.

Late afterglow matches standard models.

Abstract

The recent simultaneous detection of optical, X-ray and gamma-ray photons from GRB990123 during the burst provides the first broadband multi-wavelength characterization of the burst spectrum and evolution. Here we show that a direct correlation exists between the time-varying gamma-ray spectral shape and the prompt optical emission. This combined with the unique signatures of the time-resolved spectra of GRB990123 convincingly supports earlier predictions of the saturated Comptonization model. Contrary to other suggestions, we find that the entire continuum from optical to gamma-rays can be generated from a single source of leptons (electrons and pairs). The optical flux only appears to lag the gamma-ray flux due to the high initial Thomson depth of the plasma. Once the plasma has completely thinned out, the late time afterglow behavior of our model is the same as in standard models based on the Blandford-McKee (1976) solution.