We report on new Rossi X-ray Timing Explorer ( RXTE ) X-ray spectral analysis of bursts from SGR1806-20 , the most prolific SGR source known .
Previous studies of bursts from this source noted the remarkable lack of spectral variability both in single bursts as well as from burst to burst .
Although we find that the spectrum both within and among bursts is quite uniform we do find evidence for significant spectral changes within bursts as well as from burst to burst .
We find that optically thin thermal bremsstrahlung spectra ( OTTB ) including photoelectric absorption provide the best fits to most bursts , however , other models ( power law , Band GRB model ) can also produce statistically acceptable fits .
We confirm the existence of a rolloff in the photon number spectrum below 5 keV .
When modelled as photoelectric absorption and OTTB the inferred column is between 0.8 - 1.2 \times 10 ^ { 23 } cm ^ { -2 } .
This value is larger than the \approx 0.6 \times 10 ^ { 23 } cm ^ { -2 } inferred from ASCA observations of the persistent X-ray counterpart , but less than the \approx 10.0 \times 10 ^ { 23 } cm ^ { -2 } indicated by ICE data .