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

Abstract

We present our optical observations and multi-wavelength analysis of the GRB\,200613A detected by \texttt{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 (BIC), the data generally favor the Band+Blackbody (short as 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 constant interstellar medium (ISM). Model fitting yields the following parameters: $E_{K,iso}=(2.04_{-1.50}^{+11.8})\times 10^{53}$ erg, ${\Gamma }_0=354_{-217}^{+578}$, $p=2.09_{-0.03}^{+0.02}$, $n_{18}=(2.04_{-1.87}^{+9.71})\times 10^2$ cm${}^{-3}$, ${\theta }_j=24.0_{-5.54}^{+6.50}$ degree, ${\epsilon }_e=1.66_{-1.39}^{+4.09})\times 10^{-1}$ and ${\epsilon }_B=(7.76_{-5.9}^{+48.5})\times 10^{-6}$. In addition, we employed the public Python package \texttt{Prospector} perform a spectral energy distribution (SED) modeling of the host galaxy. The results suggest that the host galaxy is a massive galaxy ($\log (M_{\ast }/M_{\odot })=11.75_{-0.09}^{+0.10}$) with moderate star formation rate ($\mbox{SFR}=22.58^{+13.63}_{-7.22} M_{\odot}$/yr). This SFR is consistent with the SFR of $\sim 34.2M_{\odot }$ yr${}^{-1}$ derived from the [OII] emission line in the observed spectrum.

30 pages, 16 figures, accepted by ApJ