Testing for synchrotron self-absorption in GRB 970111

The time-resolved spectra of several gamma-ray bursts have shown that near the beginning of the burst, some absorption mechanism makes the spectra inc onsistent with the simple optically-thin synchrotron shock model. We fit GR B 970111, which shows strong evidence for such absorption, with a synchrotr on shock spectra suffering self-absorption. The synchrotron self-absorption shape does fit the BATSE time-evolving spectra, although it may be inconsi stent with BeppoSAX WFC data. If the turnover just below the spectral break is due to synchrotron self-absorption, a magnetic field strength of 4 10(7 ) G is required.