Unveiling the Multifaceted GRB 200613A: Prompt Emission Dynamics, Afterglow Evolution, and the Host Galaxy's Properties

Description

We present our optical observations and multiwavelength analysis of the GRB 200613A detected by the Fermi satellite. Time-resolved spectral analysis of the prompt gamma-ray emission was conducted utilizing the Bayesian block method to determine statistically optimal time bins. Based on the Bayesian Information Criterion, the data generally favor the Band+blackbody (BB) model. We speculate that the main Band component comes from the Blandford–Znajek mechanism, while the additional BB component comes from the neutrino annihilation process. The BB component becomes significant for a low-spin, high-accretion-rate black hole central engine, as evidenced by our model comparison with the data. The afterglow light curve exhibits typical power-law decay, and its behavior can be explained by the collision between the ejecta and the constant interstellar medium. Model fitting yields the following parameters: EK,iso=(2.04‑1.50+11.8)×1053 erg, Γ0=354‑217+578 , p=2.09‑0.03+0.02 , n18=(2.04‑1.87+9.71)×102 cm^‑3, θj=24.0‑5.54+6.50 degree, ϵe=1.66‑1.39+4.09)×10‑1 and ϵB=(7.76‑5.9+48.5)×10‑6 . In addition, we employed the public Python package Prospector to perform a spectral energy distribution modeling of the host galaxy. The results suggest that the host galaxy is a massive galaxy ( log(M*/M⊙)=11.75‑0.09+0.10 ) with a moderate star formation rate ( SFR=22.58‑7.22+13.63M⊙ yr^‑1). This SFR is consistent with the SFR of ∼34.2M _⊙ yr^‑1 derived from the [O II] emission line in the observed spectrum.

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