Probable evidence for a transient mega-electron volt emission line in the GRB 221023A

Abstract

Detection of spectral line in gamma-ray bursts (GRBs) is importance for studying GRB physics, as it provides insights into the composition and physical conditions of the GRB environment. However, progress in detecting X-ray or gamma-ray emission and absorption lines in GRB spectra has been relatively slow, only the narrow emission line feature of about 10 MeV found in GRB 221009A has exhibited a significance exceeding $5\sigma$. Here, we report the probable evidence of a narrow emission feature at about 2.1 mega-electron volts (MeV) in the spectrum of GRB 221023A. The highest statistical significance of this feature is observed in the time interval between 8 and 30 seconds after Fermi Gamma-Ray Burst Monitor trigger, with the chance probability value $<2.56\times 10^{-5}$ (after accounting for the look-elsewhere effect), corresponding to a Gaussian-equivalent significance $>4.20\sigma$. We interpret this feature as being generated through the de-excitation of excited electrons in the relativistic hydrogen-like high-atomic-number ions entrained in the GRB jet.

20 pages, 5 figures, 3 tables. Publication in the Nature Communications

References in corpus (30)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Swift X-ray Telescope
• The Fermi Gamma-Ray Burst Monitor
• Unsteady Outflow Models for Cosmological Gamma-Ray Bursts
• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Statistics: Handle with Care, Detecting Multiple Model Components with the Likelihood Ratio Test
• An introduction to Bayesian inference in gravitational-wave astronomy: parameter estimation, model selection, and hierarchical models
• Efficient acceleration and radiation in Poynting flux powered GRB outflows
• Trial factors for the look elsewhere effect in high energy physics
• A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope
• The Fourth Fermi-GBM Gamma-Ray Burst Catalog: A Decade of Data
• Fermi LAT Search for Internal Bremsstrahlung Signatures from Dark Matter Annihilation
• The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum
• Fermi-LAT Observations of the Gamma-ray Burst GRB 130427A
• Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705
• A Comprehensive Analysis of Fermi Gamma-ray Burst Data: II. $E_{\mathrm{p}}$-Evolution Patterns and Implications for the Observed Spectrum-Luminosity Relations
• Physics of Gamma-Ray Bursts Prompt Emission
• Prompt GRB spectra: detailed calculations and the effect of pair production
• Properties of the extremely energetic GRB~221009A from Konus-WIND and SRG/ART-XC observations
• Line Searches in Swift X-ray Spectra
• Observation of spectral lines in the exceptional GRB 221009A
• ${}^{44}\mathrm{Ti}$ ejecta in young supernova remnants
• A Search for Discrete X-ray Spectral Features in a Sample of Bright Gamma-ray Burst Afterglows
• The prompt X-ray emission of GRB011211: possible evidence of a transient absorption feature
• Nuclear de-excitation line spectrum of Cassiopeia A
• Resonant Cyclotron Radiation Transfer Model Fits to Spectra from Gamma-Ray Burst GRB870303
• Nuclear de-excitation lines as a probe of low-energy cosmic rays
• Searching for narrow absorption and emission lines in XMM-Newton spectra of gamma-ray bursts
• A Novel Model for the MeV Emission Line in GRB 221009A
• New estimation of the nuclear de-excitation line emission from the supernova remnant Cassiopeia A

Cited by in corpus (1)

• Similar Fermi-GBM sGRBs to GW/sGRB 170817A in MeV-GeV energies