  We summarize the spectral characteristics of a sample of 22 bright gamma-ray
bursts detected with the gamma-ray burst sensors aboard the satellite Ginga.
This instrument employed a proportional and scintillation counter to provide
sensitivity to photons in the 2 - 400 keV range, providing a unique opportunity
to characterize the largely unexplored X-ray properties of gamma-ray bursts.
The photon spectra of the Ginga bursts are well described by a low energy
slope, a bend energy, and a high energy slope. In the energy range where they
can be compared, this result is consistent with burst spectral analyses
obtained from the BATSE experiment aboard the Compton Observatory. However,
below 20 keV we find evidence for a positive spectral number index in
approximately 40% of our burst sample, with some evidence for a strong rolloff
at lower energies in a few events. There is a correlation (Pearson's r = -0.62)
between the low energy slope and the bend energy. We find that the distribution
of spectral bend energies extends below 10 keV. The observed ratio of energy
emitted in the X-rays relative to the gamma-rays can be much larger than a few
percent and, in fact, is sometimes larger than unity. The average for our
sample is 24%.
