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arXiv 0912.1759astro-ph.HEastro-ph.CO
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伽玛暴瞬发脉冲和快速衰变相的谱时特性

The spectral-temporal properties of the prompt pulses and rapid decay phase of GRBs

R. Willingale, F. Genet, J. Granot, P. T. O'Brien

摘要:

伽玛射线暴的瞬发辐射是目前已知的最亮的电磁辐射,但它的起源还不清楚。假设辐射来自一个薄的、超相对论性膨胀的、均匀的、在有限半径范围内的球壳,则伽玛暴的单个瞬时脉冲的通量密度可以用一个解析表达式来表示。我们提出了拟合这个解析表达式的光曲线从四个标准的Swift BAT能带和两个标准的Swift XRT能带的12个爆发。该表达式包括高纬度发射(HLE)的组件和拟合提供了一个严格的证明,HLE可以解释快速衰变阶段(RDP)的即时发射。该模型还容纳了一些方面的能量依赖的滞后和能量依赖的脉冲宽度,但有一些功能的数据没有很好地表示。有些脉冲有一个硬而窄的峰值,这是不很好地拟合或上升和衰减,这是比预期更快地使用标准指数得出的假设同步辐射从内部冲击,虽然它可能是可能的,以适应这些功能使用不同的发射机制在同一个整体框架。脉冲的亮度与脉冲光谱的峰值能量Lf ~(Epeak(1+z))^[1.8]相关,与脉冲射出后的时间Lf ~(Tf/(1 + z))^[-2.0]反相关。

英文摘要:

The prompt emission from GRBs is the brightest electromagnetic emission known yet it's origin is not understood. The flux density of individual prompt pulses of a GRB can be represented by an analytical expression derived assuming the emission is from a thin, ultra-relativistically expanding, uniform, spherical shell over a finite range of radii. We present the results of fitting this analytical expression to the lightcurves from the four standard Swift BAT energy bands and two standard Swift XRT energy bands of 12 bursts. The expression includes the High Latitude Emission (HLE) component and the fits provide a rigourous demonstration that the HLE can explain the Rapid Decay Phase (RDP) of the prompt emission. The model also accommodates some aspects of energy-dependent lag and energy-dependent pulse width, but there are features in the data which are not well represented. Some pulses have a hard, narrow peak which is not well fitted or a rise and decay which is faster than expected using the standard indices derived assuming synchrotron emission from internal shocks, although it might be possible to accommodate these features using a different emission mechanism within the same overall framework. The luminosity of pulses is correlated with the peak energy of the pulse spectrum, Lf ~ (Epeak(1+z))^1.8, and anti-correlated with the time since ejection of the pulse, Lf ~ (Tf/(1 + z))^-2.0.

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