TP-33

Redshifts from Gamma-ray Burst Spectra

Jerome James Brainerd (UAH) Robert Dwight Preece (UAH)

Gamma-ray burst spectra have two unusual characteristics: they all have approximately the same characteristic spectral energy, and they have an x-ray excess. These characteristics are consistent with a model of a power law spectrum attenuated through Compton scattering by an optically thick medium, and it has been shown that this model produces excellent fits to the observed spectra. One of the free parameters in the model is the cosmological redshift of the gamma-ray burst, so if the theory is correct, one could derive a redshift for every gamma-ray burst independent of optical observation. A comparison of the observed optical redshifts to an earlier ensemble of redshifts derived by fitting the Compton attenuation model to BATSE gamma-ray burst spectra shows that the two data sets are consistent. Comparisons of redshifts derived optically and from a fit to the gamma-ray spectrum for bursts observed both by BATSE and by optical telescopes finds agreement between the two values.