Suzaku-WAM, Konus-Wind, and Swift-BAT Observations of Prompt Emission of the High-Redshift GRB 050904

Abstract

Abstract We present the results of the high-redshift GRB 050904 at z$=$ 6.295 from joint spectral analysis among Swift-BAT, Konus-Wind, and Suzaku-WAM, covering a wide energy range of 15–5000 keV. The $\nu F_{\nu}$ spectrum peak energy, $E_{\rm peak}$, was measured at 314$^{+173}_{-89}$keV, corresponding to 2291$^{+1263}_{-634}$keV in the source frame, and the isotropic equivalent radiated energy, $E_{\rm iso}$, was estimated to be 1.04$^{+0.25}_{-0.17}$$\times$ 10$^{54}$erg. Both are among the highest values that have ever been measured. GRBs with such a high $E_{\rm iso}$ ($\sim$10$^{54}$erg) might be associated with prompt optical emission. The derived spectral and energetic parameters are consistent with the correlation between the rest-frame $E_{\rm p,i}$ and the $E_{\rm iso}$ (Amati relation), but not with the correlation between the intrinsic peak energy $E_{\rm p,i}$ and the collimation-corrected energy $E_{\gamma}$ (Ghirlanda relation), unless the density of the circumburst environment of this burst is much larger than the nominal value, as suggested by other wavelength observations. We also discuss the possibility that this burst is an outlier in the correlation between $E_{\rm p,i}$ and the peak luminosity $L_{\rm p}$ (Yonetoku relation).