Hard X-ray Spectral Investigations of Gamma-ray Bursts, 120521C and 130606A, at High-redshift z~6

Abstract

This study presents the temporal and spectral analysis of the prompt emission of two high-redshift gamma-ray bursts (GRBs), 120521C at $z\sim 6$ and 130606A at $z\sim 5.91$, which were performed using the Swift-XRT/BAT and the Suzaku-WAM simultaneously. Based on follow-up XRT observations, the longest durations of the prompt emissions were approximately $80$ s (120521C) and $360$ s (130606A) in the rest frame of each GRB, which are categorized as long-duration GRBs, but are insufficiently long compared with the predicted duration of GRBs that originate from first-generation stars. Because of the wide bandpass of the instruments covering the ranges of 15 keV--5 MeV (BAT-WAM) and 0.3 keV--5.0 MeV (XRT-BAT-WAM), we successfully determined the $\nu F_{\nu }$ peak energies $E_{\mathrm{peak}}^{\mathrm{src}}$ of $682_{-207}^{+845}$ keV and $1209_{-304}^{+553}$ keV in the rest frame, and the isotropic-equivalent radiated energies $E_{\mathrm{iso}}$ of $(8.25_{-1.96}^{+2.24})\times 10^{52}$ erg and $(2.82_{-0.71}^{+0.17})\times 10^{53}$ erg, respectively. These obtained characteristic parameters are in accordance with the well-known relation between $E_{\mathrm{peak}}^{\mathrm{src}}$ and $E_{\mathrm{iso}}$ (Amati relation). In addition, we examined the relations between $E_{\mathrm{peak}}^{\mathrm{src}}$ and the 1-s peak luminosity, $L_{\mathrm{p}}$, or the geometrical corrected radiated energy, $E_{\gamma }$, and confirmed the $E_{\mathrm{peak}}^{\mathrm{src}}$-$L_{\mathrm{p}}$ (Yonetoku) and $E_{\mathrm{peak}}^{\mathrm{src}}$-$E_{\gamma }$ (Ghirlanda) relations. The results implied that these high-redshift GRBs at $z\sim 6$, expected as having radiated from the reionization epoch, have similar properties as that of X-ray prompt emission with low-redshift GRBs.

11 pages, 6 figures; accepted to MNRAS ref. MN-16-1747-MJ.R2

References in corpus (4)

• Confirming the gamma-ray burst spectral-energy correlations in the era of multiple time breaks
• Synchrotron Self-inverse Compton Radiation From Reverse-shock on GRB120326A
• Can very massive Population III stars produce a super-collapsar?
• Sub-MeV Band Observation of a Hard Burst from AXP 1E 1547.0-5408 with the Suzaku Wide-band All-sky Monitor

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