Nuclear composition of magnetized gamma-ray burst jets

Abstract

We investigate the fraction of metal nuclei in the relativistic jets of gamma-ray bursts associated with core-collapse supernovae. We simulate the fallback in jet-induced explosions with two-dimensional relativistic hydrodynamics calculations and the jet acceleration with steady, radial, relativistic magnetohydrodynamics calculations, and derive detail nuclear composition of the jet by postprocessing calculation. We found that if the temperature at the jet launch site is above 4.7 × 10 9 K, quasi-statistical equilibrium (QSE) is established and heavy nuclei are dissociated to light particles such as 4 He during the acceleration of the jets. The criterion for the survival of metal nuclei is written in terms of the isotropic jet luminosity as L iso j < ∼ 3.9 × 10 50 (R i /10 7 cm) 2 (1 + σ i ) erg s −1 , where R i and σ i are the initial radius of the jets and the initial magnetization parameter, respectively. If the jet is initially dominated by radiation field (i.e., σ i ≪ 1) and the isotropic luminosity is relatively high (L iso j > ∼ 4 × 10 52 ergs −1 ), the metal nuclei cannot survive in the jet. On the other hand, if the jet is mainly accelerated by magnetic field (i.e., σ i ≫ 1), metal nuclei initially contained in the jet can survive without serious dissociation even for the case of high luminosity jet. If the jet contains metal nuclei, the dominant nuclei are 28 Si, 16 O, and 32 S and the mean mass number can be A ∼ 25.

Low-luminosity gamma-ray bursts as the sources of ultrahigh-energy cosmic ray nuclei

“…Note that the nuclei in the inner disk region may be photodisintegrated into free nucleons if the temperature and density are high enough [61]. This is the case for the neutrino-dominated accretion flow (NDAF) where neutrino annihilation drives the relativistic out-flow, and the disk should be composed of lighter composition dominated by protons once the quasi-statistical equilibrium (QSE) is established with temperature T 4×10 9 K [46]. Thus, in the classical fireball model, it has been shown that the jet composition of HL GRBs is likely to be dominated by protons and neutrons (see Ref.…”

“…One of the uncertainties comes from the unknown mass fraction of UHECR nuclei ejected from LL GRBs. It has been shown that the jets of LL GRBs can readily contain a significant fraction of nuclei [19,46]. In this work, we aim to give new predictions based on nuclear composition models inside the jet, considering progenitor dependencies, and examine whether they are compatible with Auger results.…”

Theories of central engine for long gamma-ray bursts

“…This is because, in the former case, matter at the central region of the star starts to move outwardly and very little matter is left at 10 s. So, the resulting amount of 56 Ni drops significantly. Tominaga et al confirmed the conclusion by 2D relativistic HD simulations [199][200][201]. In figure 8, the total ejected amount of 56 Ni is shown as a function of energy deposition rates (red curve in upper panel).…”

Hydrodynamics and Nucleosynthesis of Jet-driven Supernovae. I. Parameter Study of the Dependence on Jet Energetics

“…For the neutrino case (Liu et al 2017), the extremely high temperature at the inner boundary of the accretion disk (∼10-20 MeV) provides the necessary neutrino heat deposition as an energy source for the jet; however, the jet may not be strong enough to sustain until the stellar surface (Wei et al 2019). For the radiation case, the explosion is similar to the MHD case, but the photons may destroy most of the metal nuclei during its propagation to the surface (Shibata & Tominaga 2015). The jet stability is also closely related to the jet geometry such as the opening angle (Aloy et al 2000;Zhang et al 2003Zhang et al , 2004.…”