Steep slopes and preferred breaks in gamma-ray burst spectra: The role of photospheres and comptonization

The role of a photospheric component and of pair breakdown is examined in t he internal shock model of gamma-ray bursts. We discuss some of the mechani sms by which they would produce anomalously steep low-energy slopes, X-ray excesses and preferred energy breaks. Subrelativistic Comptonization should dominate in high comoving luminosity bursts with high baryon load, while s ynchrotron radiation dominates the power-law component in bursts which have lower comoving luminosity or have moderate to low baryon loads. A photosph ere leading to steep low-energy spectral slopes should be prominent in the lowest baryon load cases.