GRB 221009A: An Ordinary Nearby GRB with Extraordinary Observational Properties

Abstract

The gamma-ray burst GRB 221009A, known as the “brightest of all time,” is the closest energetic burst detected so far, with an energy of E γ,iso ∼ 1055 erg. This study aims to assess its compatibility with known GRB energy and luminosity distributions. Our analysis indicates that the energy/luminosity function of GRBs is consistent across various redshift intervals, and that the inclusion of GRB 221009A does not significantly impact the function at low redshifts. Additionally, our evaluation of the best-fitting result of the entire GRB sample suggests that the expected number of GRBs with energy greater than 1055 erg at a low redshift is 0.2, so that the emergence of GRB 221009A is consistent with expected energy/luminosity functions within ∼2σ Poisson fluctuation error, still adhering to the principles of small number statistics. Furthermore, we find that GRB 221009A and other energetic bursts, defined as E γ,iso ≳ 1054 erg, exhibit no significant differences in terms of distributions of T 90, minimum timescale, Amati relation, E γ,iso–E X,iso relation, L γ,iso–Γ0 relation, E γ,iso–Γ0 relation, L γ,iso–E p,i–Γ0 relation, and host galaxy properties, compared to normal long GRBs. This suggests that energetic GRBs (including GRB 221009A) and other long GRBs likely have similar progenitor systems and undergo similar energy dissipation and radiation processes. The generation of energetic GRBs may be due to more extreme central engine properties or, more likely, a rarer viewing configuration of a quasi-universal structured jet.

Observation of GRB 221009A Early Afterglow in X-Ray/Gamma-Ray Energy Bands

“…We argue that these results strongly disfavor the simple top-hat jet model but provide support to the structured jet scenario with a bright narrow core. This is also consistent with the statistical analysis results by comparing GRB 221009A with the entire GRB sample (Lan et al 2023). In this structured jet model, the narrow jet core with ultrarelativistic Lorentz factor should be surrounded by a wider jet with a lower Lorentz factor, leading to complicated temporal and spectral features (e.g., Panaitescu et al 2006;Racusin et al 2008).…”

Towards a model of photon-axion conversion in the host galaxy of GRB 221009A

“…With its unique observational appearance, the GRB 221009A gamma-ray burst [11,12] is suitable for tests of these new-physics hypotheses. Thanks to a relatively nearby, z ≈ 0.151 [13,14], location, and to precise pointing of the jet to us, it was the brightest GRB ever JCAP01(2024)016 observed [15][16][17]. Similar events are expected to be seen by a terrestrial observer once per ≳ 10 4 years only [15].…”

Constraints on axion-like particles from the observation of GRB 221009A by LHAASO

“…GRB 221009A, a gamma-ray burst (GRB) with a redshift of 0.151 [42][43][44], has been recognized as the most luminous long GRB ever observed [45][46][47]. Initially reported by Fermi-GBM [48], it was subsequently observed by multiple detectors across a wide energy band in 2022, ranging from radio to very high energy (VHE) γ-rays [49][50][51][52][53][54][55][56][57][58][59][60].…”