One of the most prominent, yet controversial associations derived from the
ensemble of prompt-phase observations of gamma-ray bursts (GRBs) is the
apparent correlation in the source frame between the peak energy Epeak) of the
nu-F(nu) spectrum and the isotropic radiated energy, Eiso. Since most gamma-ray
bursts (GRBs) have Epeak above the energy range (15-150 keV) of the Burst Alert
Telescope (BAT) on Swift, determining accurate Epeak values for large numbers
of Swift bursts has been difficult. However, by combining data from Swift/BAT
and the Suzaku Wide-band All-Sky Monitor (WAM), which covers the energy range
from 50-5000 keV, for bursts which are simultaneously detected, one can
accurately fit Epeak and Eiso and test the relationship between them for the
Swift sample. Between the launch of Suzaku in July 2005 and the end of April
2009, there were 48 gamma-ray bursts (GRBs) which triggered both Swift/BAT and
WAM and an additional 48 bursts which triggered Swift and were detected by WAM,
but did not trigger. A BAT-WAM team has cross-calibrated the two instruments
using GRBs, and we are now able to perform joint fits on these bursts to
determine their spectral parameters. For those bursts with spectroscopic
redshifts, we can also calculate the isotropic energy. Here we present the
results of joint Swift/BAT-Suzaku/WAM spectral fits for 91 of the bursts
detected by the two instruments. We show that the distribution of spectral fit
parameters is consistent with distributions from earlier missions and confirm
that Swift bursts are consistent with earlier reported relationships between
Epeak and isotropic energy. We show through time-resolved spectroscopy that
individual burst pulses are also consistent with this relationship.Comment: Accepted for publication in the Astrophysical Journa
