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arXiv 0904.1464astro-ph.HEastro-ph.COastro-ph.IMphysics.ins-det
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GRB探测器探测器对宇宙学标准烛光的可能影响

The Possible Impact of GRB Detector Thresholds on Cosmological Standard Candles

A. Shahmoradi, R. J. Nemiroff

摘要:

伽马射线暴卫星是相对低效的暗硬爆发探测器,因为它们触发光子计数,这是对硬光子的数量偏置。因此,例如,给定在检测阈值附近的相同峰值亮度的两个突发,将优先检测到暗淡的软突发而不是暗淡的硬突发。这种探测器偏差会产生或扭曲一种明显的相关性,其中越来越硬的伽马射线暴看起来越来越亮。虽然这样的相关性可能会被混淆的中间步骤,伽玛暴需要足够明亮,有他们的实际红移确定,它被发现的偏见是普遍的。这一结果是通过将各种可能的伽玛暴亮度和光谱与BATSE大面积探测器(LAD)探测阈值进行卷积的模拟得出的。分析表明,长持续时间伽玛暴的静止坐标系$νF_ν$谱峰值能量$\epi$,在没有明显的选择效应修正的情况下,不是一个好的宇宙学标准烛光。因此,$\epi$在Amati($E_{iso}-\epi$)、Ghirlanda($E_γ-\epi$)和$L_{iso}-\epi$关系等表面相关性中的出现在统计学上是真实的,但受到迄今为止未校准的GRB探测器阈值的强烈影响。

英文摘要:

GRB satellites are relatively inefficient detectors of dim hard bursts because they trigger on photon counts, which are number-biased against hard photons. Therefore, for example, given two bursts of identical peak luminosity near the detection threshold, a dim soft burst will be preferentially detected over a dim hard burst. This detector bias can create or skew an apparent correlation where increasingly hard GRBs appear increasingly bright. Although such correlations may be obfuscated by a middle step where GRBs need to be bright enough to have their actual redshifts determined, it is found that the bias is generally pervasive. This result is derived here through simulations convolving a wide variety of possible GRB brightnesses and spectra with the BATSE Large Area Detectors (LAD) detection thresholds. The presented analyses indicate that the rest-frame $νF_ν$ spectrum peak energy of long-duration GRBs, $\epi$, is not a good cosmological standard candle without significant corrections for selection effects. Therefore, the appearance of $\epi$ in seeming correlations such as the Amati ($E_{iso}-\epi$), Ghirlanda ($E_γ-\epi$), and $L_{iso}-\epi$ relations is statistically real but strongly influenced by so far uncalibrated GRB detector thresholds.

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