Maria Lopes, Armando Bernui, Wiliam S. Hipólito-Ricaldi, Camila Franco, Felipe Avila
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引用次数: 0
摘要
目的我们研究了更新的FERMI/GBM目录中伽马射线暴(GRBs)的大角度分布,以探测这些天体物理瞬变事件的统计各向同性。我们还研究了伽马射线暴通量的角度分布,以此来探索这一辐射特征是否在天空中显示出一些偏好的方向,从而暗示它们的起源。我们采用与模型无关的方法对更新的 FERMI/GBM 星表进行了方向分析。我们的结果的统计意义是通过与一大组统计上各向同性的宇宙天体样本进行比较得到的,这些样本具有与FERMI数据相同的特征。我们的分析证实,FERMIGRB 的角度分布在天球上是统计各向同性的。此外,我们还分析了 FERMIGRB 通量的方向分布,即扫描天球的一组方向上 GRB 通量的中位数,发现这一天体物理特性呈现出一种净偶极结构,其方向偏好银河系平面附近的纬度。然而,其他研究表明,这种方向偏好与银河系银河面无关,这表明 GRB 数据集及其通量偶极结构源自银河系外。有趣的是,对 BATSE 第 4 频道通量数据(即来自 BATSE 能量大于 300 keV 的 GRB)的分析表明,其偶极子方向与宇宙微波背景偶极子非常吻合。
Dipolar fluence distribution of statistically isotropic FERMI gamma-ray bursts
Aims. We investigated the large-angle distribution of the gamma-ray bursts (GRBs) from the updated FERMI/GBM catalog to probe the statistical isotropy of these astrophysical transient events. We also studied the angular distribution of the GRB fluence as a way to explore whether this radiative feature shows some preferred direction on the sky that suggest their origin.Methods. Our model-independent approach performed a directional analysis of the updated FERMI/GBM catalog. The statistical significance of our results is obtained by comparison with a large set of statistically isotropic samples of cosmic objects, with the same features of the FERMI data.Results. Our analyses confirm that the angular distribution of the FERMIGRB is statistically isotropic on the celestial sphere. Moreover, analyzing the directional distribution of the FERMIGRB fluence, that is, the median GRB fluence in a set of directions that scans the celestial sphere, we found that this astrophysical property exhibits a net dipolar structure with a directional preference for latitudes near the Galactic plane. However, additional studies show that this directional preference is not correlated with the Milky Way Galactic plane, which suggests that the GRB dataset, and its fluence dipolar structure, are extra-Galactic in origin. Interestingly, the analyses of the BATSE Channel 4 fluence data, that is, those GRBs from BATSE with energy > 300 keV, reveal that its dipole direction is very well aligned with the cosmic microwave background dipole.
期刊介绍:
Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.