Observation of spectral lines in the exceptional GRB 221009A  

作　　者：Yan-Qiu Zhang Shao-Lin Xiong Ji-Rong Mao Shuang-Nan Zhang Wang-Chen Xue Chao Zheng Jia-Cong Liu Zhen Zhang Xi-Lu Wang Ming-Yu Ge Shu-Xu Yi Li-Ming Song Zheng-Hua An Ce Cai Xin-Qiao Li Wen-Xi Peng Wen-Jun Tan Chen-Wei Wang Xiang-Yang Wen Yue Wang Shuo Xiao Fan Zhang Peng Zhang Shi-Jie Zheng 

机构地区：[1]Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Yunnan Observatories,Chinese Academy of Sciences,Kunming 650011,China [4]Center for Astronomical Mega-Science,Chinese Academy of Sciences,Beijing 100012,China [5]Key Laboratory for the Structure and Evolution of Celestial Objects,Chinese Academy of Sciences,Kunming 650216,China [6]College of Physics and Hebei Key Laboratory of Photophysics Research and Application,Hebei Normal University,Shijiazhuang 050024,China [7]Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing,Guizhou Normal University,Guiyang 550001,China [8]College of Electronic and Information Engineering,Tongji University,Shanghai 201804,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2024年第8期187-206,共20页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Key R&D Program of China(Grant Nos.2021YFA0718500,and 2023YFE0101200);the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA15360102,XDA15360300,and XDA15052700);the National Natural Science Foundation of China(Grant Nos.12273042,61234003,61434004,61504141,11673062,12393813,2333007,12027803,and 12303045);the CAS Interdisciplinary Project(Grant No.KJZD-EW-L11-04);supported by the Strategic Priority Research Program on Space Science(Grant No.XDA15360000)of the Chinese Academy of Sciences;supported by the Yunnan Revitalization Talent Support Program(Yun Ling Scholar Award)。

摘　　要：As the brightest gamma-ray burst ever observed,GRB 221009A provided a precious opportunity to explore spectral line features.In this article,we performed a comprehensive spectroscopy analysis of GRB 221009A jointly with GECAM-C and Fermi/GBM data to search for emission and absorption lines.For the first time we investigated the line feature throughout this GRB including the most bright part where many instruments suffered problems,and identified prominent emission lines in multiple time intervals.The central energy of the Gaussian emission line evolves from about 37 to 6 MeV,with a nearly constant ratio(about 10%)between the line width and central energy.Particularly,we find that both the central energy and the energy flux of the emission line evolve with time as a power law decay with power law index of–1 and–2,respectively.We suggest that the observed emission lines most likely origin from the blue-shifted electron positron pair annihilation 511 ke V line.We find that a standard high latitude emission scenario cannot fully interpret the observation,thus we propose that the emission line comes from some dense clumps with electron positron pairs traveling together with the jet.In this scenario,we can use the emission line to directly,for the first time,measure the bulk Lorentz factor of the jet(Γ)and reveal its time evolution(i.e.,Γ~t^(-1))during the prompt emission.Interestingly,we find that the flux of the annihilation line in the co-moving frame keeps constant.These discoveries of the spectral line features shed new and important lights on the physics of GRB and relativistic jet.

关 键 词：GRB GRB 221009A emission line 

分 类 号：P172.3[天文地球—天文学]