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arXiv 1209.4647astro-ph.HEastro-ph.COphysics.data-an
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长伽玛暴的多元拟合光度函数和世界模型

A Multivariate Fit Luminosity Function and World Model for Long GRBs

Amir Shahmoradi

摘要:

本文提出了宇宙学长持续时间(II型)伽马射线暴(LGRB)的光度函数、静止帧谱相关和分布可以很好地描述为多元对数正态分布。这一结果是基于对迄今为止最大的伽马射线暴目录中的LGRB的时间和光谱变量的仔细选择、分析和建模:2130个BATSE GRB,同时考虑到检测阈值和可能的选择效应。导出了各向同性峰值亮度(Liso)、总各向同性发射(Eiso)、时间积分谱峰能量(Epkz)和持续时间(T90 z)的联合静止坐标系分布的约束条件。所提出的分析提供了证据,证明BATSE探测器遗漏了相对较大比例的LGRB,Eiso延伸到~ 10^49 [erg],观测到的谱峰能量(Epk)低至~ 5 [keV]。静止帧持续时间T90 z < 1 [s]或静止帧持续时间T90 < 2 [s]的LGRB似乎是罕见事件(发生概率<0.1%)。该模型预测了相当强的,但非常显着的相关性(rho=0.58 \pm 0.04)之间的Eiso和Epkz的LGRB。还预测了Liso和Eiso与T90 z的强相关性以及Liso和Epkz之间的中等相关性。发现的相关性的强度和意义鼓励了对潜在机制的探索,尽管削弱了它们作为高红移暗能量状态方程探针的能力。所提出的分析有利于-但不一定-宇宙率的BATSE LGRB跟踪金属丰度演化符合截止~ 0.2-0.5,假设没有亮度红移演化。

英文摘要:

It is proposed that the luminosity function, the rest-frame spectral correlations and distributions of cosmological Long-duration (Type-II) Gamma-Ray Bursts (LGRBs) may be very well described as multivariate log-normal distribution. This result is based on careful selection, analysis and modeling of LGRBs' temporal and spectral variables in the largest catalog of Gamma-Ray Bursts available to date: 2130 BATSE GRBs, while taking into account the detection threshold and possible selection effects. Constraints on the joint rest-frame distribution of the isotropic peak luminosity (Liso), total isotropic emission (Eiso), the time-integrated spectral peak energy (Epkz) and duration (T90z) of LGRBs are derived. The presented analysis provides evidence for a relatively large fraction of LGRBs that have been missed by BATSE detector with Eiso extending down to ~ 10^49 [erg] and observed spectral peak energies (Epk) as low as ~ 5 [keV]. LGRBs with rest-frame duration T90z < 1 [s] or observer-frame duration T90 < 2 [s] appear to be rare events (<0.1% chance of occurrence). The model predicts a fairly strong but highly significant correlation (rho=0.58 \pm 0.04) between Eiso & Epkz of LGRBs. Also predicted are strong correlations of Liso & Eiso with T90z and moderate correlation between Liso & Epkz. The strength and significance of the correlations found, encourage the search for underlying mechanisms, though undermine their capabilities as probes of Dark Energy's equation of state at high redshifts. The presented analysis favors -- but does not necessitate -- a cosmic rate for BATSE LGRBs tracing metallicity evolution consistent with a cutoff ~ 0.2-0.5, assuming no luminosity-redshift evolution.

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