ARGO实验中“双前峰面”事例探测高能γ射线暴的灵敏度研究

发布时间:2019-01-09 18:56
【摘要】:γ射线暴是一种在短时间内能量剧烈爆发的天文学现象,是人们研究宇宙线起源的重要手段。到2015年12月31日为止,卫星实验在keV~MeV能段已经探测到了 5000多个γ射线暴,但对能量大于10 GeV的高能γ射线暴,目前还没有观测到确定的结果。高能γ射线暴不仅能够提供γ射线暴产生机制的直接证据,而且能检验当前存在争议的γ射线暴的模型,因而其研究具有重要意义。为了得到γ射线暴从低能到高能的完整信息,必须联合卫星实验和地面实验。位于羊八井观测站的ARGO和ASγ实验凭借其高海拔、宽视场、大面积等特点在探测高能γ射线暴方面占据着一席之地,值得注意的是,其中ARGO实验中的"双前峰面"事例具有降低阈能值、提高灵敏度的独特优势,为高能γ射线暴的探测提供了一种全新的方式。首先,本文对"双前峰面"事例探测高能γ射线暴的灵敏度进行模拟。结果表明:在持续时间为1s、天顶角为10°且红移为0时,"双前峰面"事例探测E10GeV γ射线暴的流强为10-4~10-3erg/cm2。与此同时,"双前峰面"事例的灵敏度在Emax30GeV时高于"触发"事例的,因此利用"双前峰面"事例寻找高能γ射线暴存在巨大潜能。其次,分析Fermi卫星从2008年到2015年期间观测到的1756个γ射线暴,利用Band模型将这些γ射线暴的能谱延伸到羊八井地面实验的能区范围内,计算其到达羊八井地面实验中的流强。结果表明:对于在羊八井视场范围内且光子能量在GeV能区的Fermi γ暴,若不考虑河外背景光子的吸收效应,ARGO实验运行期间内,在其灵敏度范围内的有3个;新升级的ASy实验运行期间内,在其灵敏度范围内的有4个。这些结果为羊八井地面实验(包括"双前峰面"事例)与卫星γ暴的符合寻找提供重要信息。最后,结合ARGO实验中GRB100225703的"双前峰面"事例数据与Fermi卫星的数据来符合寻找高能γ射线暴。结果表明:显著性最高的事例团作为本底涨落的概率(Pb)为1.72×10-6,相当于高斯分布的4.643σ,但考虑到实验次数后,其超出不足以认定为γ射线暴。
[Abstract]:纬-ray burst is an astronomical phenomenon which erupts violently in a short period of time and is an important means to study the origin of cosmic rays. Up to December 31, 2015, more than 5000 纬-ray bursts have been detected in the keV~MeV energy range in satellite experiments, but no definite results have been observed for high energy 纬-ray bursts with energy greater than 10 GeV. High energy 纬-ray bursts can not only provide direct evidence of the mechanism of 纬-ray bursts, but also test the models of 纬-ray bursts which are currently controversial, so their research is of great significance. In order to obtain the complete information of 纬-ray bursts from low energy to high energy, it is necessary to combine satellite experiments and ground experiments. The ARGO and AS 纬 experiments at Yangbajing observation Station occupy a place in detecting high energy 纬 -ray bursts due to their characteristics of high altitude, wide field of view and large area. The "double front peak" in ARGO experiment has the unique advantage of reducing threshold energy and improving sensitivity, which provides a new way for detecting high energy 纬 -ray bursts. First, the sensitivity of "double front peak" cases for detecting high energy 纬-ray bursts is simulated. The results show that when the duration is 1 s, the zenith angle is 10 掳and the red shift is 0, the current intensity of the "double front peak" event for detecting E10GeV 纬 -ray bursts is 10 ~ (-4) ~ 10 ~ (-3) erg / cm ~ (2). At the same time, the sensitivity of "double front peak" event is higher than that of "trigger" event at Emax30GeV, so there is great potential to use "double front peak" event to find high energy 纬 -ray burst. Secondly, 1756 纬-ray bursts observed by Fermi satellite from 2008 to 2015 are analyzed. The energy spectrum of these 纬-ray bursts is extended to the energy range of the surface experiment of Yangbajing by using the Band model, and the current intensity in the surface experiment of Yangbajing is calculated. The results show that for the Fermi 纬 bursts in the range of view field of Yangbajing and the photon energy in the GeV region, if the photon absorption effect of the background outside the river is not taken into account, there are three Fermi 纬 bursts in the range of sensitivity during the operation of the ARGO experiment. During the running of the newly upgraded ASy experiment, there are four in the range of sensitivity. These results provide important information for the coincidence search between the surface experiments of Yangbajing (including the case of "double front peak") and satellite 纬-ray bursts. Finally, combining the "double front peak" case data of GRB100225703 in ARGO experiment with the data of Fermi satellite, we can find the high energy 纬 -ray bursts. The results show that the probability of the most significant event cluster as the background fluctuation is 1.72 脳 10 ~ (-6), which is equivalent to 4.643 蟽 of Gao Si's distribution, but considering the number of experiments, its excess is not enough to be considered as 纬 -ray burst.
【学位授予单位】:西南交通大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:O571.323

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