The centrifugal acceleration is due to the rotating poloidal magnetic field in the magnetosphere creates the electric field which is orthogonal to the magnetic field. Charged particles with finite cyclotron radii can move along the electric field and receive energy. Centrifugal acceleration pushes particles to the periphery, where their azimuthal velocity reaches the light speed. We have calculated particle trajectories by numerical and analytical methods. The maximum obtained energies depend on the parameter of the particle magnetization $ κ$, which is the ratio of rotation frequency of magnetic field lines in the magnetosphere $ Ω_F $ to non-relativistic cyclotron frequency of particles $ ω_c $, $ κ= Ω_F /ω_c << 1 $, and from the parameter $ α$ which is the ratio of toroidal magnetic field $ B_T $ to the poloidal one $ B_P $, $ α= B_T / B_P $. It is shown that for small toroidal fields, $ α<κ^{1/4} $, the maximum Lorentz factor $ γ_m $ is only the square root of magnetization, $ γ_m = κ^{-1/2} $, while for large toroidal fields, $ α>κ^{1/4} $, the energy increases significantly, $ γ_m = κ^{-2/3} $. However, the maximum possible acceleration, $ γ_m = κ^{-1} $, is not achieved in the magnetosphere. For a number of active galactic nuclei, such as M87, maximum values of Lorentz factor for accelerated protons are found. Also for special case of Sgr. A* estimations of the maximum proton energy and its energy flux are obtained. They are in agreement with experimental data obtained by HESS Cherenkov telescope.
Acceleration of protons in the active galactic nuclei is considered. The largest energy is achieved by protons during centrifugal acceleration in the magnetosphere of the central machine. When the proton accelerated in the magnetosphere of a black hole approaches light cylinder surface, acceleration occurs mainly in the azimuthal direction, i.e. the acceleration is centrifugal. In this paper the acceleration of a proton having smaller synchrotron losses compared to the electron is considered. As a proton experiences the highest energy increase while accelerating near the light surface, a parti…
In this paper we study relativistic dynamics of charged particles co-rotating with prescribed trajectories, having the shape of dipolar magnetic field lines. In particular, we consider the role of the drag force caused by the photon field the forming of equilibrium positions of the charged particles. Alongside a single particle approach we also study behaviour of ensemble of particles in the context of stable positions. As we have shown, together they create surfaces where particles are at stable equilibrium positions. In this paper we examine these shapes and study parameters they depend on. …
In this paper we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process. For this purpose we study three major configurations of the field lines: the straight line; the Archimede's spiral and the dipolar field line configuration. By analysing dynamics of particles sliding along the field lines in the equatorial plane we have found several interesting features of motion. In particular, it has been shown th…
In this paper we study efficiency of particle acceleration in the magnetospheres of stellar mass black holes. For this purpose we consider the linearized set of the Euler equation, continuity equation and Poisson equation respectively. After introducing the varying relativistic centrifugal force, we show that the charge separation undergoes the parametric instability, leading to generation of centrifugally excited Langmuir waves. It is shown that these waves, via the Langmuir collapse damp by means of the Landau damping, as a result energy transfers to particles accelerating them to energies o…
Magnetic B-stars often exhibit circularly polarized radio emission thought to arise from gyrosynchrotron emission by energetic electrons trapped in the circumstellar magnetosphere. Recent empirical analyses show that the onset and strength of the observed radio emission scale with both the magnetic field strength and the stellar rotation rate. This challenges the existing paradigm that the energetic electrons are accelerated in the current sheet between opposite-polarity field lines in the outer regions of magnetised stellar winds, which includes no role for stellar rotation. Building on recen…
Supermassive stars (SMSs), with masses $>10^5$ M$_\odot$, have been proposed as the possible progenitors of the most extreme supermassive black holes observed at redshifts $z>6-7$. In this scenario ('direct collapse'), a SMS accretes at rates $>0.1$ M$_\odot$ yr$^{-1}$ until it collapses to a black hole via the general-relativistic (GR) instability. Rotation plays a crucial role in the formation of such supermassive black hole seeds. The centrifugal barrier appears as particularly strong in this extreme case of star formation. Moreover, rotation impacts sensitively the stability of SMSs agains…
Coupled Time-Dependent Proton Acceleration and Leptonic-Hadronic Radiation in Turbulent Supermassive Black Hole Coronae
Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；National and Kapodistrian University of Athens（雅典国立卡波迪斯特里安大学）；Queen’s University（女王大学）；Arthur B. McDonald Canadian Astroparticle Physics Research Institute（阿瑟·B·麦克唐纳加拿大高能天体粒子物理研究所）；Perimeter Institute for Theoretical Physics（理论物理前沿研究所）
We study the force balance and resulting acceleration of gas in general relativity basing on simulations of accretion on a stellar-mass, non-rotating black hole. We compare properties of acceleration in an optically thin, radiatively inefficient disk, and in an optically thick, super-critical disk accreting at 10 times the Eddington rate. We study both the average forces acting at given location and forces acting on a gas parcel along its trajectory. We show that the acceleration is not a continuous process - in most cases gas is accelerated only in short-lasting episodes. We find that in the …
The detection of rapidly variable gamma-ray emission in active galactic nuclei has generated renewed interest in magnetospheric particle acceleration and emission scenarios. In order to explore its potential, we study the possibility of steady gap acceleration around the null surface of a rotating black hole magnetosphere. We employ a simplified (1D) description along with the general relativistic expression of Gauss's law, and we assume that the gap is embedded in the radiation field of a radiatively inefficient accretion flow. The model is used to derive expressions for the radial distributi…
In this paper we consider relativistic effects of rotation in the magnetospheres of $γ$-ray pulsars. The paper reviews the progress achieved in this field during the last three decades. For this purpose we examine direct centrifugal acceleration of particles and corresponding limiting factors: constraints due to the curvature radiation and the inverse Compton scattering of electrons against soft photons. Based on the obtained results generation of parametrically excited Langmuir waves and the corresponding Landau-Langmuir-centrifugal drive is studied.
Proton Acceleration by Collisionless Shocks in Supermassive Black Hole Coronae: Implications for High-Energy Neutrinos
The University of Osaka（大阪大学）；Institute of Laser Engineering, The University of Osaka（大阪大学激光工程研究所）；Shibaura Institute of Technology（芝浦工业大学）；RIKEN（理化学研究所）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo（东京大学宇宙线起源研究教育中心（WPI））
The Langmuir-Landau-Centrifugal Drive (LLCD), that can effectively "convert" gravitational energy into particles, is explored as a driving mechanism responsible for the extreme thermal luminosity acquired by some active galactic nuclei (AGN). For this purpose we consider equations governing the process of heating of AGN magnetospheres. In particular, we examine the Fourier components of the momentum equation, the continuity equation and the Poisson equation in the linear approximation and estimate the growth rate of the centrifugally excited electrostatic waves and the increment of the Langmui…
We study particle acceleration and radiative processes in Blazar jets under recurring conditions set by gravitational perturbations in supermassive binary systems. We consider the action from a companion orbiting a primary black hole of $\sim 10^8 \, M_{\odot}$, and perturbing its relativistic jet. We discuss how such conditions induce repetitive magneto-hydrodynamic stresses along the jet, and affect its inner electron acceleration and radiative processes. Specifically, we study how macroscopic perturbations related to increased jet "magnetization" end up into higher radiative outputs in the …
Modeling YSO Jets in 3D I: Highly Variable Asymmetric Magnetic Pressure-Driven Jets in the Polar Cavity from Toroidal Fields Generated by Inner Disk Accretion
Supermassive black holes lying in the center of galaxies can launch relativistic jets of plasma along their polar axis. The physics of black-hole jets is a very active research topic in astrophysics, owing to the fact that many questions remain open on the physical mechanisms of jet launching, of particle acceleration in the jet, and on the radiative processes. In this work I focus on the last item, and present a review of the current understanding of radiative emission processes in supermassive-black-hole jets.
Evidence for high-energy astrophysical PeV neutrinos has been found in the IceCube experiment from an analysis with a 7.5 year (2010 - 2017) data. Active galactic nuclei (AGN) are among the most prominent objects in the universe, and are widely speculated to be emitters of ultra-high-energy (UHE) cosmic rays with proton domination. Based on the standard two-step LLCD mechanism of particle acceleration, a transformation of energy occurs from AGN's central super-massive black hole (SMBH) rotation to high-energy protons. Protons can be accelerated up to $\sim 0.1$ EeV energies and above, and migh…
Supermassive stars (SMSs) collapsing via the general-relativistic (GR) instability are invoked as the possible progenitors of supermassive black holes. Their mass and angular momentum at the onset of the instability are key in many respects, in particular regarding the possibility for observational signatures of direct collapse. Here, we study the stability of rotating, rapidly accreting SMSs against GR and derive the properties of these stars at death. On the basis of hylotropic structures, relevant for rapidly accreting SMSs, we define rotation profiles under the assumption of local angular …
NGC 253 is a nearby starburst galaxy in the Sculptor group located at a distance of 3.5 Mpc that has been suggested by some authors as a potential site for cosmic-ray acceleration up to ultra-high energies. Its nuclear region is heavily obscured by gas and dust, which prevents establishing whether or not the galaxy harbours a supermassive black hole coexisting with the starburst. Some sources have been proposed in the literature as candidates for an active nucleus. In this work, we aim at determining the implications that the presence of a supermassive black hole at the nucleus of NGC 253 migh…
Recent observations with ALMA have revealed evidence for non-thermal synchrotron emission from the core regions of two nearby Seyfert galaxies. This suggests that the coronae of accretion disks in active galactic nuclei (AGNs) can be conducive to the acceleration of non-thermal electrons, in addition to the hot, thermal electrons responsible for their X-ray emission through thermal Comptonization. Here we investigate the mechanism of such particle acceleration, based on observationally inferred parameters for AGN disk coronae. One possibility to account for the observed non-thermal electrons i…
Cosmic rays accelerated to ultra-high energies (E>4x10^19 eV) in electric fields in accretion discs around supermassive black holes are discussed. Particle injection spectra are assumed to be harder than those formed in acceleration on shock fronts. It turned out that cosmic rays with injection spectra supposed contribute a little in the particle flux detected with ground-based arrays. But in the extragalactic space particle generate a noticeable flux of the diffuse gamma-ray emission compared with the data obtained with the Fermi LAT instrument (onboard the Fermi space observatory). The inten…
Production and acceleration mechanisms of ultra-high-energy cosmic rays (UHECRs) of energy $>10^{20}$eV, clearly beyond the GZK-cutoff limit remain unclear that points to exotic nature of the phenomena. Recent observations of extragalactic neutrino may indicate the source of UHECRs being an extragalactic supermassive black hole (SMBH). We demonstrate that ultra-efficient energy extraction from rotating SMBH driven by the magnetic Penrose process (MPP) could indeed foot the bill. We envision ionization of neutral particles, such as neutron beta-decay, skirting close to the black hole horizon th…
School of Natural Sciences, Institute for Advanced Study（自然科学院，高等研究院）；Rudolf Peierls Centre for Theoretical Physics, University of Oxford（鲁道夫·皮尔斯理论物理中心，牛津大学）
Electron-positron pair creation near sub-Eddington accretion rate black holes is believed to be dominated by the Breit-Wheeler process (photon-photon collisions). The interacting high energy photons are produced when unscreened electric fields accelerate leptons either in coherent, macroscopic gaps or in incoherent structures embedded in the turbulent plasma flow. The latter type of acceleration results in a drizzle of pair production sourced by photons from the background radiation field whose energies are near the pair-production threshold. In this work, we use radiation GRMHD simulations to…
We demonstrate that particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. Some examples of such flows include spontaneous turbulent reconnection and decaying magnetohydrodynamic (MHD) turbulence, where magnetic field relaxes to a lower-energy configuration and transfers part of its energy to kinetic motions. The opposite process, such as dynamo, will actually result in the net cooling of particles by the curvature drift. Being very generic, this acceleration mechanism is likely to be responsible in production of non-thermal particle distrib…
A novel model of particle acceleration in the rotating magnetospheres of active galactic nuclei (AGN) and pulsars is constructed. The particle energies may be boosted up to enormous energies in a several step mechanism. In the first stage, the Langmuir waves are centrifugally excited and amplified by means of a parametric process that efficiently pumps rotational energy to excite electrostatic fields. By considering the pulsars it is shown that the Langmuir waves very soon Landau damp on the relativistic electrons already present in a magnetosphere. It has been found that the process is so eff…
Probing Boson Clouds with Supermassive Black Hole Binaries
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；School of Physics Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Center for High Energy Physics, Peking University（北京大学高能物理中心）
In this paper, we investigate the acceleration in relativistic jets of high-energy proton preaccelerated in the magnetosphere of a supermassive black hole. The proton reaches maximum energy when passing the total potential difference of $U$ between the jet axis and its periphery. This voltage is created by a rotating black hole and transmitted along magnetic field lines into the jet. It is shown that the trajectories of proton in the jet are divided into three groups: untrapped, trapped and not accelerated. Untrapped particles are not kept by poloidal and toroidal magnetic fields inside the je…
Effects of High-Energy Particles on Accretion Flows onto a Supermassive Black Hole
我们研究了高能粒子对超大质量黑洞吸积流的影响以及逃逸粒子如质子、中子、γ射线和中微子的光度。我们制定了一个一维模型的两个组件的吸积流组成的热粒子和高能粒子，假设释放的能量的一部分被转换为加速的高能粒子。热分量由流体动力学控制，而高能粒子服从扩散-对流方程的矩方程。通过求解这些方程的时间演化，我们得到了平流主导流的稳态解。即使高能粒子的压力超过了热压力，高能粒子对流动结构的影响也很小。对于逃逸质子带走几乎所有释放能量的模型，高能粒子的影响足以使流在内部区域具有开普勒角速度。我们计算这些稳定的解决方案的逃逸粒子的光度。逃逸粒子可以提取从大约$10^{-4}\dot M c^2$到$10^{-2}\dot M c^2$的能量，其中$\dot M$是质量吸积率。逃逸粒子的亮度取决于注入洛伦兹因子、质量吸积率和扩散系数等参数。我们还讨论了逃逸粒子对相对论性喷流产生的影响。
We investigate a model of ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the General Relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can be then determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both c…
We propose the model of the global structure of the electromagnetic fields in the Fermi bubbles (FBs), which makes possible the proton regular acceleration up to ultra-high energies. The poloidal and the toroidal magnetic fields, as well as the radial electric field, turn to have a structure similar to fields that exist in jets ejected out from active galactic nuclei (AGN). A powerful source of relativistic particles observed in the centre of the Galaxy and associated with the rotating supermassive black hole (SMBH) Sgr A* can energize the FB and keeps its active for a long time. The absence o…
In many astrophysical scenarios the charge of the black hole is often neglected due to unrealistically large values of the charge required for the Reissner-Nordström spacetime metric. However, black holes may possess small electric charge due to various selective accretion mechanisms. In this paper we investigate the effect of a small hypothetical electric charge of a Schwarzschild black hole on the ionization of a freely falling neutral particle and subsequent escape of the ionized particle from the black hole. We show that the energy of ionized particle can grow ultra-high and discuss distin…
A rotating star with a monopole (or split monopole) magnetic field gives the simplest, prototype model of a rotationally driven stellar wind. Winds from compact objects, in particular neutron stars, carry strong magnetic fields with modest plasma loading, and develop ultra-relativistic speeds. We investigate the relativistic wind launched from a dense, gravitationally bound, atmosphere on the stellar surface. We first examine the problem analytically and then perform global kinetic plasma simulations. Our results show how the wind acceleration mechanism changes from centrifugal (magnetohydrody…
Multi-frequency gravitational wave (GW) observations are useful probes of the formation processes of coalescing stellar-mass binary black holes (BBHs). We discuss the phase drift in the GW inspiral waveform of the merging BBH caused by its center-of-mass acceleration. The acceleration strongly depends on the location where a BBH forms within a galaxy, allowing observations of the early inspiral phase of LIGO-like BBH mergers by the Laser Interferometer Space Antenna (LISA) to test the formation mechanism. In particular, BBHs formed in dense nuclear star clusters or via compact accretion disks …
Discovery of minute-scale polarization angle rotation in a supermassive black hole jet
University of Crete（克里特大学）；Foundation for Research and Technology-Hellas（希腊研究与技术基金会）；The Pennsylvania State University（宾夕法尼亚州立大学）；Institute of Astrobiology, University of Crete（克里特大学天体生物学研究所）；Chalmers University of Technology（查尔姆斯理工大学）；Friedrich-Alexander Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡弗里德里希·亚历山大大学）
The BL Lac PG 1553+113 has been continuously monitored in gamma rays with Fermi-LAT for over 9 years. Its updated light curve now includes 5 iterations of a main pattern comprising a high peak and a longer trough, with a period P \sim 2.2 yr. Our analysis of 2015-2017 data confirms the occurrence in January 2017 of a new peak fitting in the previous trend. In addition, we identify secondary peaks ("twin peaks") that occur in closely symmetric pairs on both sides of most main peaks, including the last one; their occurrence is supported by correlated X-ray outbursts. We stress that the above fea…
