Nuclear Composition of Gamma-Ray Burst Fireballs

By A. Beloborodov. 2002

167 citations recorded by the source corpus.

We study three processes that shape the nuclear composition of gamma-ray burst (GRB) fireballs: (1) neutronization in the central engine, (2) nucleosynthesis in the fireball as it expands and cools, and (3) spallation of nuclei in subsequent internal shocks. The fireballs are found to have a neutron excess and a marginally successful nucleosynthesis. They are composed of free nucleons, α-particles, and deuterium. A robust result is the survival of a significant neutron component, which has important implications. First, as shown in previous works, neutrons can lead to observable multi-GeV neutrino emission. Second, as we show in an accompanying paper, neutrons impact the explosion dynamics at radii up to 1017 cm and change the mechanism of the GRB afterglow emission.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7c4a6966cc8b52c4e0deb3542f1e5521856b6762

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

The physics of gamma-ray bursts & relativistic jets (2014, background): “Neutrons that survive these collisions travel to larger distances before decaying and that could affect the afterglow radiation from GRBs (Beloborodov, 2003a; Fan et al., 2005a).”
Collisional mechanism for gamma‐ray burst emission (2009, background): “4 and 5 in Beloborodov 2003).”
Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers (2014, unknown): “…∼ 1010–1012 g cm−3 and T ∼ 10–100 GK ∼1–10 MeV, respectively) such conditions imply low values of the electron fraction, Yβe ≡ Ye(ρ, T , μν = 0) ∼ 0.1−0.2, for which electrons are moderately degenerate (see, e.g. Ruffert et al. 1997; Beloborodov 2003; Chen & Beloborodov 2007; Arcones et al. 2010).”
Composition of the Innermost Core-Collapse Supernova Ejecta (2004, background): “…the investigation of the r -process in the neutrino wind of a protoneutron star (Qian & Woosley 1996; Thompson et al. 2001); and the cases where emission terms dominate or where the neutrinos are in thermal equilibrium have been analysed in a study of gamma-ray burst fireballs (Beloborodov 2003).”
Two-dimensional hydrodynamic core-collapse supernova simulations with spectral neutrino transport - I. Numerical method and results for a 15 solar mass star (2005, background): “…outflow becomes proton-rich because the neutron-to-proton mass difference favors positron captures, e++n→ p+ν̄e, against electron captures, e−+p→ n+ νe, when the electron degeneracy is low, i.e. the electron chemical potential µe <∼ kT (Beloborodov 2003; Liebendörfer et al. 2003).”
Short-hard gamma-ray bursts (2007, background): “If neutrons are present in the fireball as well, as expected if the engine is driven by accretion onto a compact object (e.g., Beloborodov, 2003b), these will be dragged by nucleon collisions along with the protons up to high Lorentz factor and may affect the evolution of the fireball at late times…”
Neutrino heating near hyper-accreting black holes (2010, background): “(1) The neutrino cooled discs are nearly in β-equilibrium: the rates of the two reactions in equation (1) are practically equal, which determines the value of Ye(ρ, T) (Imshennik, Nadezhin & Pinaev 1967; Beloborodov 2003).”
The late time evolution of gamma-ray bursts: ending hyperaccretion and producing flares (2006, unknown): “…and this provides favorable initial conditions for the subsequent production of a baryon-poor fireball [e.g., Fuller, Pruet & Abazajian (2000); Beloborodov (2003); Vlahakis & Königl (2003); Mészáros (2002)], or a magnetically dominated “cold fireball” [Lyutikov & Blandford (2002)], though…”
Dynamical Evolution of Neutrino-cooled Accretion Disks: Detailed Microphysics, Lepton-driven Convection, and Global Energetics (2005, background): “As noted by (Beloborodov 2003), a distinction needs to be made to determine the equilibrium composition depending on the optical depth of the material (the determinatio of the opacities is presented in § 2.4).”
Delayed outflows from black hole accretion tori following neutron star binary coalescence (2013, background): “100 km), weak interactions are faster than the viscous time, and the electron fraction reaches its equilibrium value given the local density and temperature (e.g., Beloborodov 2003).”
Long-term GRMHD simulations of neutron star merger accretion discs: implications for electromagnetic counterparts (2018, background): “In particular, degeneracy strongly suppresses the positron density, because pairs are created in the exponential tail of the thermal distribution above the Fermi sphere (e.g., Beloborodov 2003).”
Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “…the disk can still be cooled by thermal neutrino emission (Popham et al. 1999; Narayan et al. 2001; Kohri & Mineshige 2002; Di Matteo et al. 2002; Beloborodov 2003; Kohri et al. 2005; Kawanaka & Mineshige 2007; Chen & Beloborodov 2007), a process that affects the lepton number of the disk in…”
Time-dependent models of accretion discs formed from compact object mergers (2008, methodology): “A neutron-rich outflow may alter the jet’s dynamics and the prompt and afterglow emission from that of the standard GRB fireball model (e.g., Derishev et al. 1999; Beloborodov 2003b; Rossi et al. 2006).”
Neutrino-cooled Accretion Disks around Spinning Black Holes (2006, background): “1 and 2 in Beloborodov 2003a) applies with a high accuracy.”
Neutron-powered precursors of kilonovae (2014, background): “4 Beloborodov (2003) we estimate thatYe could be raised to∼ 0.3 or above given the temperatures and densities corresponding to m≈ 10−4M⊙.”