Reviewing $Epeak$ relations with Swift and Suzaku data

In recent years several authors have derived correlations between gamma‐ray burst (GRB) spectral peak energy $(Epeak)$ and either isotropic‐equivalent radiated energy $(Eiso)$ or peak luminosity $(Liso).$ Since these relationships are controversial, but could provide redshift estimators, it is important to determine whether bursts detected by Swift exhibit the same correlations. Swift has greatly added to the number of GRBs for which redshifts are known and hence $Eiso$ and $Liso$ could be calculated. However, for most bursts it is not possible to adequately constrain $Epeak$ with Swift data alone since many GRBs have $Epeak$ above the energy range (15–150 keV) of the Swift Burst Alert Telescope (BAT). Therefore we have analyzed the spectra of 78 bursts (31 with redshift) which were detected by both Swift/BAT and the Suzaku Wide‐band All‐sky Monitor (WAM), which covers the energy range 50–5000 keV. For most bursts in this sample we can precisely determine $Epeak$ and for bursts with known redshift we can compare how the $Epeak$ relations for the Swift/Suzaku sample compare to earlier published results.