【作者】 张海明；

【导师】 陆睿静； 梁恩维； 张晋；

【作者基本信息】 广西大学 ， 理论物理， 2017， 硕士

【摘要】 本论文首先简述活动星系核的基本特征及近年来的观测进展,然后介绍围绕耀变体的GeV光变特征开展的研究工作。我们系统分析了26个耀变体的费米/大视场探测器观测数据(约8年)。首先是对耀变体3C 454.3进行了细致的分析,我们发现:(1)其能谱随流量的增强而变硬,(2)光变时标约为几天,(3)多波段的光变研究表明射电(15 GHz)与伽玛射线波段的光变可能源于不同的辐射区。然后对另外25个耀变体也进行了分析,结果显示:与3C 454.3相似,它们均表现出辐射谱随流量增强而变硬的特征。我们也探究它们光变的起源,这26个源的光变可能都是由不同的随机过程及辐射区物理属性的改变共同引起的。除此之外,我们也探究当前关注度比较高的点源S5 0716+714和PMN J0948+0022的伽玛射线光变曲线,发现它们分别存在约350天和480天的准周期信号。活动星系核和伽玛暴都存在相对论性喷流。我们对比研究了耀变体3C 454.3与GRBs 090618、140508A中喷流洛伦兹因子(r)的演化,发现这三者的r演化模式各不相同。对于3C 454.3,r跟随伽玛射线流量增强而变大,这可能表明伽玛射线流量的改变是由多普勒增强效应所致;对于GRB 140508A,r随流量减少而减少,这可能是源于GRB140508A中心引擎活动的衰减;而对于GRB 090618,r先增加后几乎保持恒定,这可能表明相对论火球在光球位置处仍然处于加速状态,之后进入滑行阶段。更多还原

【Abstract】 In the first chapter of this thesis,the basic characteristics and the observational progress of active galactic nucleus in recent years are presented.Subsequent chapters focus on introducing my graduate study about the variability characteristics of blazars at GeV band.We systematically analyze about 8-year Fermi/LAT observation data for 26 blazar sources.For the analysis on 3C 454.3,it is found that:(1)the behavior of spectral evolution at gamma-ray band is "harder when brighter",(2)the typical variability timescale at gamma-ray band is several days,(3)the variability at 15 GHz differs from that at gamma-ray band,which may be caused by their emitting regions being different.For the analysis of other 25 sources,their spectral evolutions all behave "harder when brighter",similar to that of 3C 454.3.We also investigate the origin of their light curves and find that their light curves should be caused by both the different statistical noise processes and the possible systematic variations for all 26 cases.In addition,we also use the Lomb-Scargle method to analyze the gamma-ray light curves of S5 0716 + 714 and PMN J0948 + 0022,and find that there are possible periods about 350 days for S5 0716 + 714 and 480 days for PMN J0948 + 0022.Furthermore,we study the Lorentz factor(Γ)evolution patterns of relativistic jets of 3C 454.3,GRB 090168 and GRB 140508A and find that their Γ evolution patterns are different from each other.For 3C 454.3,a pattern of r-tracking-gamma-ray flux is clearly found,likely indicating that the observed gamma-ray flares are being due to the Doppler boosting effect to the jet emission.The clear decrease evolution pattern of Γ in GRB 140508A suggests the decay of the fireball central engine.And the increasing-to-coasting evolution pattern of Γ in GRB 090618 may indicate that the relativistic fireball is still being accelerated at the place of photonsphere and then coming into the coasting phase.更多还原