Neutrino‐cooled Accretion Disks around Spinning Black Holes

Chen, Wenxin; Beloborodov, Andrei M.

doi:10.1086/508923

Cited by 334 publications

(487 citation statements)

References 29 publications

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“…Figure 3 shows the disk once it has fully self-regulated itself into this mildly degenerate state (μ e =k B T ∼ 1). The inner disk remains neutron-rich (Y e ≈ 0.1) over the course of the simulation up to radii r ≲ 60 km (≲14 gravitational radii), consistent with previous one-dimensional models of neutrino-cooled disks [26,67].…”

Section: Prl 119 231102 (2017) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 87%

Out of Neutron Star Rubble Comes Gold

Rosswog

2017

Physics

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The merger of binary neutron stars, or of a neutron star and a stellar-mass black hole, can result in the formation of a massive rotating torus around a spinning black hole. In addition to providing collimating media for γ-ray burst jets, unbound outflows from these disks are an important source of mass ejection and rapid neutron capture (r-process) nucleosynthesis. We present the first three-dimensional generalrelativistic magnetohydrodynamic (GRMHD) simulations of neutrino-cooled accretion disks in neutron star mergers, including a realistic equation of state valid at low densities and temperatures, self-consistent evolution of the electron fraction, and neutrino cooling through an approximate leakage scheme. After initial magnetic field amplification by magnetic winding, we witness the vigorous onset of turbulence driven by the magnetorotational instability (MRI). The disk quickly reaches a balance between heating from MRI-driven turbulence and neutrino cooling, which regulates the midplane electron fraction to a low equilibrium value Y e ≈ 0.1. Over the 380-ms duration of the simulation, we find that a fraction ≈20% of the initial torus mass is unbound in powerful outflows with asymptotic velocities v ≈ 0.1c and electron fractions Y e ≈ 0.1-0.25. Postprocessing the outflows through a nuclear reaction network shows the production of a robust second-and third-peak r process. Though broadly consistent with the results of previous axisymmetric hydrodynamical simulations, extrapolation of our results to late times suggests that the total ejecta mass from GRMHD disks is significantly higher. Our results provide strong evidence that postmerger disk outflows are an important site for the r process.

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Section: Prl 119 231102 (2017) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 87%

Out of Neutron Star Rubble Comes Gold

Rosswog

2017

Physics

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“…As commonly recognized, the pressure from nucleons should dominate in the inner region of the NDAF when the mass accretion rate is greater than 0.01 M s −1 (see, e.g., Chen & Beloborodov 2007;Liu et al 2007;Kawanaka & Mineshige 2007). As shown above, the nucleonic EoS is subject to change A129, page 4 of 5 if we include more microscopic physics beyond the simple standard free-gas model.…”

Section: Resultsmentioning

confidence: 84%

“…As shown above, the nucleonic EoS is subject to change A129, page 4 of 5 if we include more microscopic physics beyond the simple standard free-gas model. Such a simple model is widely used in the NDAF or collapsar models (see, e.g., Popham et al 1999;MacFadyen et al 2001;Chen & Beloborodov 2007;Liu et al 2007). For an improved study, a detailed database of the resulting pressure with the change in the temperature, the density, and the neutrino opacity should be built.…”

Section: Resultsmentioning

confidence: 99%

Revisiting the hot matter in the center of gamma-ray bursts and supernovae

Liu

2013

A&A

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Aims. Hot matter with nucleons can be produced in the inner region of the neutrino-dominated accretion flow in gamma-ray bursts or during the proto-neutron star birth in successful supernovae. The composition and equation of state of the matter depend on the dynamic β equilibrium under various neutrino opacities. The strong interaction between nucleons may also play an important role. We plan to extend the previous studies by incorporating these two aspects in our model. Methods. The modification of the β-equilibrium condition from neutrino optically thin to thick was modeled by an equilibrium factor χ ranging between the neutrino-freely-escaping case and the neutrino-trapped case. We employed the microscopic BruecknerHartree-Fock approach extended to the finite temperature regime to study the interacting nucleons. Results. We show the composition and chemical potentials of the hot nuclear matter for different densities and temperatures at each stage of β equilibrium. We also compare our realistic equation of states with those of the free-gas model. We find that it is important to properly describe the neutrino opacity and the strong interaction between nucleons, and they should be taken into account in model calculations.

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“…However, as matter flows inward to smaller radii where the temperature is higher, neutrino cooling is increasingly important, possibly even causing the disk to transition to a geometrically thin configuration (e.g., Di Matteo et al 2002). A straightforward calculation shows that a thin disk is obtained inside a critical radius R ν given by (Chen & Beloborodov 2007; see also Metzger et al 2008, their Equation (11))…”

Section: Disk Propertiesmentioning

confidence: 99%

Nuclear Dominated Accretion Flows in Two Dimensions. I. Torus Evolution With Parametric Microphysics

Fernández

Metzger

2013

ApJ

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We explore the evolution of radiatively inefficient accretion disks in which nuclear reactions are dynamically important ("Nuclear Dominated Accretion Flows" or NuDAFs). Examples of such disks are those generated by the merger of a white dwarf with a neutron star or black hole, or by the collapse of a rotating star. Here, we present two-dimensional hydrodynamic simulations that systematically explore the effect of adding a single nuclear reaction to a viscous torus. The equation of state, anomalous shear stress, and nuclear reactions are given parametric forms. Our results point to the existence of two qualitatively different regimes of NuDAF evolution: (1) steady accretion with quiescent burning or (2) detonation of the disk. These outcomes are controlled primarily by the ratio Ψ of the nuclear energy released to the enthalpy at the burning radius. Disks detonate if Ψ exceeds a critical value Ψ crit ∼ 1, and if burning occurs in regions where neutrino cooling is unimportant. Thermonuclear runaways are seeded by the turbulent mixing of hot ash with cold fuel at the burning front. Disks with Ψ < Ψ crit do not explode, but instead power a persistent collimated outflow of unbound material composed primarily of ash, with a mass-loss rate that increases with Ψ. We discuss the implications of our results for supernova-like counterparts from astrophysical events in the NuDAF regime. In particular, detonations following a white dwarf-neutron star merger could account for some subluminous Type Ia supernovae, such as the class defined by SN 2002cx.

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Neutrino‐cooled Accretion Disks around Spinning Black Holes

Cited by 334 publications

References 29 publications

Out of Neutron Star Rubble Comes Gold

Out of Neutron Star Rubble Comes Gold

Revisiting the hot matter in the center of gamma-ray bursts and supernovae

Nuclear Dominated Accretion Flows in Two Dimensions. I. Torus Evolution With Parametric Microphysics

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