The Astrophysical Journal Letters (Jan 2025)

Candidate Spectral Lines at 6 and 15 MeV from GRB 200829A and GRB 160905A

  • Tong-Lei Liao,
  • Shuo Xiao,
  • Shao-Lin Xiong,
  • Yan-Qiu Zhang,
  • Wang-Chen Xue,
  • Jiao-Jiao Yang,
  • Zheng-Huo Jiang,
  • Shu-Xu Yi,
  • Zhen Zhang,
  • Shuang-Nan Zhang

DOI
https://doi.org/10.3847/2041-8213/ade4b8
Journal volume & issue
Vol. 987, no. 1
p. L7

Abstract

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The discoveries of the evolving spectral line in gamma-ray burst (GRB) 221009A provide valuable information for understanding its extreme physical environment and emission mechanisms. In this work, we perform a comprehensive search for 3941 GRBs recorded in the Fermi/Gamma-ray Burst Monitor (GBM) from 2008 July to 2025 February; although no confirmed spectral lines are found, two spectral line candidates at ∼15 and ∼6 MeV in GRB 160905A and GRB 200829A are identified, respectively. Interestingly, the latter’s rest-frame line energy ∼13 MeV at redshift z = 1.25 is similar to that of GRB 221009A at z = 0.151. If this is true, it implies that they may share a common physical origin, possibly linked to blueshifted electron–positron annihilation processes within relativistic jets. Finally, this comprehensive search reveals no >5 σ significant line features across the GBM GRB sample, with only two candidates at ∼3 σ level. These results place meaningful constraints on the peculiarity and possible origin of the spectral line observed in GRB 221009A.

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