Time-Resolved Spectroscopy With The Batse Large Area Detectors: High-Energy Behavior

For burst spectral continuum studies, the BATSE Large Area Detectors (LADs) have better count statistics over their entire energy range than the Spectroscopy Detectors (SDs). The LADs also have moderate energy resolution, which means that most continuum spectral models will be well-determined over nearly 2 decades in energy. With the SD data, Ford et al. have shown that bursts exhibit a variety of evolutionary behavior in E(peak), the energy of the peak in vF(v). By using LAD data for bright bursts such as those studied by Ford et al., we can track the evolution of any spectral parameter with finer time resolution and we can extend the analysis to fainter events, for a sample size of 110. Here, we concentrate upon the time evolution of the high-energy power law component (E(beta)) above E(peak), when it can be determined. The one noticeable feature from the survey is a negative correlation of high-energy power law index (steepening of spectra) with intensity during bright peaks of 21 of the bursts. In 25 of the others, the power-law evolution generally follows the same hard-to-soft pattern throughout a burst as the other spectral parameters. The absence of a hard power-law component in a group of 7 'super-soft' bursts indicates one extreme of the distribution of power-law indices across the entire sample.