Viscous evolution of a massive disk surrounding stellar-mass black holes in full general relativity

Sho Fujibayashi; Masaru Shibata; Shinya Wanajo; Kenta Kiuchi; Koutarou Kyutoku; Yuichiro Sekiguchi

doi:10.1103/PhysRevD.102.123014

paper

Viscous evolution of a massive disk surrounding stellar-mass black holes in full general relativity

arXiv:2009.03895 · doi:10.1103/PhysRevD.102.123014

Abstract

Long-term viscous neutrino-radiation hydrodynamics simulations in full general relativity are performed for a massive disk surrounding spinning stellar-mass black holes with mass $M_{BH} = 4$ , $6$ , and $10 M_{⊙}$ and initial dimensionless spin $χ \approx 0.8$ . The initial disk is chosen to have mass $M_{disk} \approx 0.1$ or $3 M_{⊙}$ as plausible models of the remnants for the merger of black hole-neutron star binaries or the stellar core collapse from a rapidly rotating progenitor, respectively. For $M_{disk} \approx 0.1 M_{⊙}$ with the outer disk edge initially located at $r_{out} \sim 200$ km, we find that $15$ %- $20$ % of $M_{disk}$ is ejected and the average electron fraction of the ejecta is $⟨ Y_{e} ⟩ = 0.30$ - $0.35$ as found in the previous study. For $M_{disk} \approx 3 M_{⊙}$ , we find that $\approx 10$ %- $20$ % of $M_{disk}$ is ejected for $r_{out} \approx 200$ - $1000$ km. In addition, $⟨ Y_{e} ⟩$ of the ejecta can be enhanced to be $≳ 0.4$ because the electron fraction is increased significantly during the long-term viscous expansion of the disk with high neutrino luminosity until the mass ejection sets in. Our results suggest that not heavy $r$ -process elements but light trans-iron elements would be synthesized in the matter ejected from a massive torus surrounding stellar-mass black holes. We also find that the outcomes of the viscous evolution for the high-mass disk case is composed of a rapidly spinning black hole surrounded by a torus with a narrow funnel, which appears to be suitable for generating gamma-ray bursts.

arXiv comment25 pages, 17 figures

Viscous evolution of a massive disk surrounding stellar-mass black holes in full general relativity

Abstract

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