Thermal and non-thermal emission from a peculiar long-duration GRB 211211A

Abstract

Long-duration GRB 211211A that lacks a supernova emission even down to very stringent limits at such a low redshift z = 0.076 and associate with kilonova emission, suggest that its physical origin is from binary compact stars merger. By re-analyzing its data observed with the GBM on board Fermi mission, we find that both time-integrated and time-resolved spectra can be fitted well by using Band plus blackbody (Band+BB) model in the prompt emission. The bulk Lorentz factors (Γ ph ) of the outflow can be inferred by invoking the observed thermal emission at photosphere radius within a pure fireball model, and find out that the temporal evolution of Γ ph seems to be tracking with the light curve. The derived values of Γ ph are also consistent with the Γ ph -L γ,iso /E γ,iso correlations that had been found in other bursts. Moreover, we also calculate the magnetization factor σ 0 in the central engine and σ ph at the photosphere radius within the framework of hybrid jet model, and find that the values of both 1 + σ 0 and 1 + σ ph are larger than 1 for different time slices. It suggests that at least the Poynting-flux component is indeed existent in the outflow. If this is the case, one possible physical interpretation of thermal and non-thermal emissions in GRB 211211A is from the contributions of both ν ν annihilation and the Blandford-Znajek mechanisms in the relativistic jet when a stellar mass black hole reside in the central engine.

Long-duration Gamma-ray Burst and Associated Kilonova Emission from Fast-spinning Black Hole--Neutron Star Mergers

“…Very recently, the observations of an lGRB (i.e., GRB 211211A) associated with a kilonova emission at a redshift z = 0.0763 (luminosity distance D L ≈ 350 Mpc) was reported by a few groups (Rastinejad et al 2022;Yang et al 2022;Xiao et al 2022;Gompertz et al 2022b;Mei et al 2022;Zhang et al 2022;Chang et al 2022). The burst was characterized by a spiky main emission (ME) phase with a duration of ∼ 13 s, an EE phase lasting ∼ 55 s, and a temporal lull between these two phases.…”

Long-duration Gamma-Ray Burst and Associated Kilonova Emission from Fast-spinning Black Hole–Neutron Star Mergers

“…Very recently, observations of an lGRB (i.e., GRB 211211A) associated with a kilonova emission at a redshift z = 0.0763 (luminosity distance D L ≈ 350 Mpc) were reported by a few groups (Chang et al 2022;Gompertz et al 2022b;Mei et al 2022;Rastinejad et al 2022;Xiao et al 2022;Yang et al 2022;Zhang et al 2022). The burst was characterized by a spiky main emission (ME) phase, with a duration of ∼13 s, an EE phase lasting ∼55 s, and a temporal lull between these two phases.…”