Time-evolution of Peak Energy and Luminosity Relation within Pulses for GRB 061007: Probing Fireball Dynamics

Abstract

We perform a time-resolved spectral analysis of bright, long Gamma-ray burst GRB 061007 using Suzaku/WAM and Swift/BAT. Thanks to the large effective area of the WAM, we can investigate the time evolution of the spectral peak energy, Et_peak and the luminosity Lt_iso with 1-sec time resolution, and we find that luminosity Lt_iso with 1-sec time resolution, and we find that the time-resolved pulses also satisfy the Epeak-Liso relation, which was found for the time-averaged spectra of other bursts, suggesting the same physical conditions in each pulse. Furthermore, the initial rising phase of each pulse could be an outlier of this relation with higher Et_peak value by about factor 2. This difference could suggest that the fireball radius expands by a factor of 2-4 and/or bulk Lorentz factor of the fireball is decelerated by a factor of 4 during the initial phase, providing a new probe of the fireball dynamics in real time.

21 pages, 16 figures, accepted for publication in PASJ

References in corpus (7)

• Hard X-ray Detector (HXD) on Board Suzaku
• The Ep,i - Eiso correlation in GRBs: updated observational status, re-analysis and main implications
• In-Orbit Performance of the Hard X-ray Detector on board Suzaku
• Thermalization in Relativistic Outflows and the Correlation between Spectral Hardness and Apparent Luminosity in Gamma-ray Bursts
• Unstable GRB photospheres and electron-positron annihilation lines
• Extreme Properties Of GRB061007: A Highly Energetic OR Highly Collimated Burst?
• Closure Relations for Electron-Positron Pair-Signatures in Gamma-Ray Bursts

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• Possible existence of Ep-Lp and Ep-Eiso correlations for Short Gamma-Ray Bursts with a factor 5 to 100 dimmer than those for Long Gamma-Ray Bursts
• Lorentz Factor Constraint from the very early external shock of the gamma-ray burst ejecta
• Very High Lorentz Factor Fireballs and Gamma-Ray Burst Spectra
• The $E_{\mathrm{p}}$-Flux Correlation in the Rising and Decaying Phases of Gamma-Ray Burst Pulses: Evidence for Viewing Angle Effect?
• Spectral components in the bright, long GRB 061007: properties of the photosphere and the nature of the outflow
• GRB 090618: different pulse temporal and spectral characteristics within a burst