Maciej Jabłoński, Aleksandra Kotek, Miljenko Čemeljić, Włodek Kluźniak
We perform resistive and viscous MHD simulations of axial jet launching from a magnetized thin accretion disk around a supermassive black hole. We compare the forces in our pseudo-Newtonian simulations for the Paczyński-Wiita and Kluźniak-Lee potentials. The results will help to find magnetic field configurations and physical parameters conducive to jet launching.
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We write down and apply the linearized fluid and gravitational equations consistent with pseudo-Newtonian simulations, whereby Newtonian hydrodynamics is used with a pseudo-Newtonian monopole and standard Newtonian gravity for higher multipoles. We thereby eliminate the need to use mode function matching to identify the active non-radial modes in pseudo-Newtonian core-collapse supernova simulations, in favor of the less complex and less costly mode frequency matching method. In doing so, we are able to measure appropriate boundary conditions for a mode calculation.
We have modeled hydrodynamical tori in the Klu{ź}niak-Lee pseudo-Newtonian potential. The tori in equilibrium were perturbed with uniform sub-sonic velocity fields: vertical, radial and diagonal respectively, and allowed to evolve in time. We identify the eigenmodes corresponding to those of slender tori. The results of our simulations are relevant to the investigation of high-frequency quasi-periodic oscillations observed in stellar-mass black hole binaries.
Pseudo-Newtonian potentials are a tool often used in theoretical astrophysics to capture some key features of a black-hole space-time in a Newtonian framework. As a result, one can use Newtonian numerical codes, and Newtonian formalism in general, in an effective description of important astrophysical processes such as accretion onto black holes. In this paper we develop a general pseudo-Newtonian formalism which pertains to the motion of particles, light, and fluids in stationary space-times. In return, we are able to assess the applicability of the pseudo-Newtonian scheme. The simplest and m…
We obtain equilibrium solutions for rotating compact stars including the special relativistic effects. The gravity is assumed to be Newtonian, but we used the active mass density, which takes into account all the energies such as motions of the fluids, internal energy, pressure energy in addition to the rest mass energy, in computing the gravitational potential using Poisson's equation. Such a treatment could be applicable to the neutron stars with relativistic motions or relativistic equation of state. We applied the Hachisu's self-consistent field (SCF) method to find spheroidal as well as t…
Pseudo-Newtonian gravitational potential introduced in spherically symmetric black-hole spacetimes with a repulsive cosmological constant is tested for equilibrium toroidal configurations of barotropic perfect fluid orbiting the black holes. Shapes and potential depths are determined for the marginally stable barotropic tori with uniform distribution of specific angular momentum, using both the pseudo-Newtonian and fully relativistic approach. For the adiabatic (isoentropic) perfect fluid, temperature profiles, mass-density and pressure profiles and total masses of pseudo-Newtonian and relativ…
Tests of general relativity in pseudo-Newtonian approach
本文通过伪牛顿方法测试广义相对论经典测试，展示其在强场引力中的应用与局限性。
$g$-mode of neutron stars in pseudo-Newtonian gravity
本研究在伪牛顿引力框架下研究中子星的$g$-模，发现一种处理方式能以约1%的误差近似广义相对论解，为低成本分析含一级相变EOS的中子星振荡及CCSN模拟提供有效工具。
The Johannsen-Psaltis spacetime describes a rotating black hole with parametric deviations from the Kerr metric. By construction this spacetime explicitly violates the no-hair theorems. Rotating black hole solutions in any modified theory of gravity could be written in terms of the Johannsen-Psaltis metric. We examined the accretion of gas onto a black hole described by the static limit of this spacetime. We employed a potential that generalises the Paczynski-Wiita potential to the static Johannsen-Psaltis metric. Our analysis utilised a recent pseudo-Newtonian formulation of the dynamics arou…
Pseudo-Newtonian simulation of a thin accretion disk around a Reissner-Nordström naked singularity
本文首次用伪牛顿势模拟Reissner-Nordström裸奇点周围的薄吸积盘，发现吸积在零重力球附近形成环状结构，并指出该旋转环可能是裸奇点的观测特征。
Neutron star oscillations in pseudo-Newtonian gravity
本研究使用纯牛顿方法和三种伪牛顿形式研究中子星振荡，发现Zha等人提出的“Case A+lapse”形式能将1.4太阳质量中子星的基本径向模式频率近似到百分之几十以内，并将非径向四极f模式频率近似到百分之几以内。
Pseudo-Newtonian potential for accretion disks in a modified gravity spacetime around the black hole and underlying properties
本文提出了一种伪牛顿势，用于在修改引力框架下研究黑洞周围的吸积盘，通过比较轨道特性验证其有效性，展示了在强引力天体物理中的应用价值。
A pseudo-Newtonian stationary circumbinary slim disk model
本文建立纳入双星潮汐力矩的伪牛顿稳态绕双星slim盘模型，通过与薄盘和单黑洞AGN比较，揭示密度、光谱、力矩及轨道收缩效应。
General form for Pseudo-Newtonian Potentials, imitating Schwarzschild geodesics
本文提出了一种通用的伪牛顿势形式，能够模仿Schwarzschild测地线的关键特征，包括最内稳定圆轨道、近日点进动和边际束缚圆轨道。
Strong magnetic fields modify particle motion in the curved space-time of spinning black holes and change the stability conditions of circular orbits. We study conditions for magnetocentrifugal jet launching from accretion disks around black holes, whereby large scale black hole lines anchored in the disk may fling tenuous coronal gas outward. For a Schwarzschild black hole, magnetocentrifugal launching requires that the poloidal component of magnetic fields makes an angle less than $60^\circ$ to the outward direction at the disk surface, similar to the Newtonian case. For prograde rotating di…
Bridging relativistic jets from black hole scales to long-term electromagnetic radiation distances: A moving-mesh general relativistic hydrodynamics code with the HLLC Riemann solver
提出了广义相对论移动网格框架JET，结合HLLC黎曼求解器，首次实现相对论喷流从黑洞尺度诞生到牛顿耗散阶段的全过程自洽模拟。
We present a comprehensive analytic model of relativistic jet propagation in expanding homologous media (ejecta). This model covers the entire jet evolution as well as a range of configurations that are relevant to binary neutron star mergers. These include low and high luminosity jets, unmagnetized and mildly magnetized jets, time-dependent luminosity jets, and Newtonian and relativistic head velocities. We also extend the existing solution of jets in a static medium to power-law density media with index $α<5$. Our model provides simple analytic formulae (calibrated by 3D simulations) for the…
We develop a numerical hydrodynamics code using a pseudo-Newtonian formulation that uses the weak field approximation for the geometry, and a generalized source term for the Poisson equation that takes into account relativistic effects. The code was designed to treat moderately relativistic systems such as rapidly rotating neutron stars. The hydrodynamic equations are solved using a finite volume method with High Resolution Shock Capturing (HRSC) techniques. We implement several different slope limiters for second order reconstruction schemes and also investigate higher order reconstructions. …
Based on the conserved Hamiltonian for a test particle, we have formulated a Newtonian analogue of Kerr spacetime in the `low energy limit of the test particle motion' that, in principle, can be comprehensively used to describe general relativistic (GR) features of Kerr spacetime, however, with less accuracy for high spin. The derived potential, which has an explicit velocity dependence, contains the entire relativistic features of corresponding spacetime including the frame dragging effect, unlike other prevailing pseudo-Newtonian potentials (PNPs) for the Kerr metric where such an effect is …
We present full-time-domain, moving-mesh, relativistic hydrodynamic simulations of jets launched from the center of a massive progenitor star and compute the resulting synchrotron light curves for observers at a range of viewing angles. We follow jet evolution from ignition inside the stellar center, propagation in the stellar envelope and breakout from the stellar surface, then through the coasting and deceleration phases. The jet compresses into a thin shell, sweeps up the circumstellar medium, and eventually enters the Newtonian phase. The jets naturally develop angular and radial structure…
Chaotic dynamics of off-equatorial orbits around pseudo-Newtonian compact objects with dipolar halos
本文利用广义伪牛顿势研究偶极晕致密天体周围倾斜轨道的混沌动力学，发现混沌程度随倾角增大而增强（存在阈值），随Kerr参数增大而减弱，并揭示了阈值与系统混沌性的关联。
Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions, which in turn come from the underlying dynamics. Thus, an accurate description of the flow which includes hydrodynamics and radiative transfer is a must to interpret the observational results. In the case of non-rotating black holes, Pseudo-Newtonian description of surrounding space-time enables one to make a significant progress in predicting spectral and timing properties. This formalism is lacking for spinning black holes. In this paper, we show that there exists an exact…
A generalized Newtonian potential is derived from the geodesic motion of test particles in Schwarzschild spacetime. This potential reproduces several relativistic features with higher accuracy than commonly used pseudo-Newtonian approaches. The new potential reproduces the exact location of the marginally stable, marginally bound, and photon circular orbits, as well as the exact radial dependence of the binding energy and the angular momentum of these orbits. Moreover, it reproduces the orbital and epicyclic angular frequencies to better than 6%. In addition, the spatial projections of general…
In an early work the Rossby Wave Instability (RWI) has been proposed to explain variability thought to originate in the close vicinity of black-holes but this was done in the pseudo-Newtonian approach. Here we present the first general relativistic hydrodynamics simulations of this instability not only proving its theorized existence in a full general relativistic (GR) environment but also studying the effect of the strong gravity on the instability. To that end we performed a set of simulations increasingly closer to the black hole with our new GR version of the MPI-AMRVAC code.This allows us…
Collimated and spinning fireballs for ultra-relativistic jets: long vs short Gamma-ray bursts by angular momentum and mass ratio
本研究探究伽马射线暴喷流前身旋转恒星系统的引力坍缩，分析引力结合能转化形成火球的过程，发现J/M比值影响火球准直度与喷流张角，推测其是区分长短暴的关键，并推导了火球物理量的内禀关联。
We study the relativistic accretion flow around a generic stationary axisymmetric space-time and obtain an effective potential ($Φ^{\rm eff}$) that accurately mimics the general relativistic features of Kerr black hole having spin $0\le a_k <1$. Considering the accretion disc confined around the equatorial plane of a rotating black hole and using the relativistic equation of state, we examine the properties of the relativistic accretion flow and compare it with the same obtained form semi-relativistic as well as non-relativistic accretion flows. Towards this, we first investigate the transonic…
Numerical simulation of common envelope stage in close binary systems: comparison between Newtonian and modified gravity
本文利用移动网格代码 AREPO 模拟白矮星与红巨星的共包层演化，通过伪势方法引入修正引力，并与牛顿引力结果比较以寻找潜在观测效应。
The dynamical system studied in previous papers of this series, namely a bound time-like geodesic motion in the exact static and axially symmetric space-time of an (originally) Schwarzschild black hole surrounded by a thin disc or ring, is considered to test whether the often employed "pseudo-Newtonian" approach (resorting to Newtonian dynamics in gravitational potentials modified to mimic the black-hole field) can reproduce phase-space properties observed in the relativistic treatment. By plotting Poincaré surfaces of section and using two recurrence methods for similar situations as in the r…
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