Gamma-ray emission from high Galactic latitude globular clusters
Gamma-ray emission from high Galactic latitude globular clusters
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高银河纬度球状星团的伽马射线发射
DOI：
10.1093/mnras/sty2150
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发表时间：
2018
影响因子：
4.8
通讯作者：
Lloyd S
中科院分区：
文献类型：
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作者：
Lloyd S
我们分析了8年的PASS 8费米-LAT数据，在60 MeV-300 GeV的能量范围内，从30个高银河系纬度的球状星团。其中六个球状星团的TS > 25，NGC 6254首次被探测到伽马射线明亮。最重要的检测是著名的球状星团47 Tuc，我们产生了一个精致的光谱适合这个对象与对数抛物线模型。NGC 6093、NGC 6752和NGC 6254都有坚硬的扁平幂律模型。NGC 7078最符合软实力定律，而NGC 6218最符合硬的、破碎的实力定律。这种多样的光谱模型表明，除了传统的毫秒脉冲星解释外，球状星团内还有多种伽马射线源类型。我们确定了球状星团核心的扩散X射线发射和伽马射线发射之间的对应关系。这种联系表明，球状星团中的伽马射线发射也可能来自未解析的X射线源或相对论性电子群，可能是由毫秒双星产生的。对更多伽马射线明亮球状星团的X射线观测将允许确定漫射X射线和伽马射线发射之间的函数关系。
We analyse 8 yr of PASS 8Fermi-LAT data, in the 60 MeV–300 GeV energy range, from 30 high Galactic latitude globular clusters. Six of these globular clusters are detected with a TS > 25, with NGC 6254 being detected as gamma-ray bright for the first time. The most significant detection is of the well-known globular cluster 47 Tuc, and we produce a refined spectral fit for this object with a log parabola model. NGC 6093, NGC 6752, and NGC 6254 are fitted with hard, flat power-law models. NGC 7078 is best fitted with a soft power law, and NGC 6218 is best fitted with a hard, broken power law. This variety of spectral models suggests that there is a variety of gamma-ray source types within globular clusters, in addition to the traditional millisecond pulsar interpretation. We identify a correspondence between diffuse X-ray emission in globular cluster cores and gamma-ray emission. This connection suggests that gamma-ray emission in globular clusters could also arise from unresolved X-ray sources or a relativistic electron population, perhaps generated by the millisecond pulsars. X-ray observations of further gamma-ray bright globular clusters would allow a functional relationship to be determined between diffuse X-ray and gamma-ray emission.