Significant cocoon emission and photosphere duration stretching in GRB 211211A: a burst from a neutron star - black hole merger

Abstract

The radiation mechanism (thermal photosphere or magnetic synchrotron) and the progenitor of gamma-ray burst (GRB) are under hot debate. Recently discovered, the prompt long-duration ($\sim$ 10 s, normally from the collapse of massive stars) property of GRB 211211A strongly conflicts with its association with a kilonova (normally from the merger of two compact objects, NS-NS, NS-BH, or NS-WD, duration $\lesssim$ 2 s). In this paper, we find the probability photosphere model with a structured jet can satisfactorily explain this peculiar long duration, through the duration stretching effect ($\sim$ 3 times) on the intrinsic longer ($\sim$ 3 s) duration of NS-BH (neutron star and black hole) merger, the observed empirical 2SBPL spectrum (with soft low-energy index $\alpha$ of $\sim$ -1) and its evolution. Also, much evidence of the NS-BH merger origin is found, especially the well fit of the afterglow-subtracted optical-NIR light curves by the significant thermal cocoon emission and the sole thermal red kilonova component. Finally, a convincing new explanation for the X-ray afterglow plateau is revealed.

38 pages, 17 figures, 2 tables. Under review at Nature Communications

References in corpus (13)

• Asymptotic Equivalence of Bayes Cross Validation and Widely Applicable Information Criterion in Singular Learning Theory
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• A Kilonova Following a Long-Duration Gamma-Ray Burst at 350 Mpc
• A nearby long gamma-ray burst from a merger of compact objects
• Temporal Evolution Of Thermal Emission From Relativistically Expanding Plasma
• Quasi-blackbody component and radiative efficiency of the prompt emission of gamma-ray bursts
• Different progenitors of short hard gamma-ray bursts
• The case for a minute-long merger-driven gamma-ray burst from fast-cooling synchrotron emission
• Tight multi-messenger constraints on the neutron star equation of state from GW170817 and a forward model for kilonova light curve synthesis
• The width of gamma-ray burst spectra
• Constraints on the circumburst environments of short gamma-ray bursts
• Black hole-neutron star coalescence: effects of the neutron star spin on jet launching and dynamical ejecta mass
• Evidence of Photosphere Emission Origin for Gamma-Ray Burst Prompt Emission