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arXiv 1307.7618astro-ph.HE
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长短伽玛暴的变率时标

Variability Time Scales of Long and Short GRBs

P. N. Bhat

摘要:

伽马射线暴(GRB)是一种能量极高的事件,会产生高度不同的光变曲线。光变曲线被认为是由反映伽玛射线暴中心引擎活动的内部冲击引起的。因此,他们的时间研究可能会导致对伽玛射线暴中心引擎及其演变的理解。光变曲线变化时间尺度是一个有趣的参数,大多数模型都将其归因于物理起源,中央引擎活动、团状环爆介质或相对论性湍流。我们开发了一种统计方法来估计GBM探测到的长和短GRB的GRB最小变率时标(MVT)。我们发现短暴的MVT明显短于长暴的MVT,这支持了前者有一个更紧凑的中心引擎的可能性。我们还发现,用这种方法估计的MVT与拟合脉冲的最短上升时间是一致的。因此,我们使用拟合的脉冲上升时间来研究突发变化时间尺度的演变。变化时间与探测到的最高能量光子相结合,反过来又与内部发动机发射的相对论壳层的最小体积洛伦兹因子有关。%利用这一点,我们涉及到伽玛射线暴光谱的演变的变化时间尺度的演变。

英文摘要:

Gamma-ray bursts (GRB) are extremely energetic events and produce highly diverse light curves. Light curves are believed to be resulting from internal shocks reflecting the activities of the GRB central engine. Hence their temporal studies can potentially lead to an understanding of the GRB central engine and its evolution. The light curve variability time scale is an interesting parameter which most models attribute to a physical origin e.g., central engine activity, clumpy circum-burst medium, or relativistic turbulence. We develop a statistical method to estimate the GRB minimum variability time scale (MVT) for long and short GRBs detected by GBM. We find that the MVT of short bursts is distinctly shorter than that of long GRBs supporting the possibility of a more compact central engine of the former. We also find that MVT estimated by this method is consistent with the shortest rise time of the fitted pulses. Hence we use the fitted pulse rise times to study the evolution of burst variability time scale. Variability time coupled with the highest energy photon detected in turn related to the minimum bulk Lorentz factor of the relativistic shell emitted by the inner engine. %Using this we relate the GRB spectral evolution to the evolution of the variability time scale.

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