We perform global three-dimensional (3D) radiation-hydrodynamic (RHD) simulations of out- flow from supercritical accretion flow around a 10 Msun black hole. We only solve the outflow part, starting from the axisymmetric 2D simulation data in a nearly steady state but with small perturbations in a sinusoidal form being added in the azimuthal direction. The mass accretion rate onto the black hole is ~10^2 L_E/c^2 in the underlying 2D simulation data and the outflow rate is ~10 L_E/c^2 (with LE and c being the Eddington luminosity and speed of light, respectively). We first confirm the emergence of clumpy outflow, which was discovered by the 2D RHD simulations, above the photosphere located at a few hundreds of Schwarzschild radii (r_S) from the central black hole. As prominent 3D features we find that the clumps have the shape of a torn sheet, rather than a cut string, and that they are rotating around the central black hole with a sub-Keplerian velocity at a distance of ~10^3 r_S from the center. The typical clump size is ~30 r_S or less in the radial direction, and is more elongated in the angular directions, ~hundreds of r_S at most. The sheet separation ranges from 50 to 150 r_S. We expect stochastic time variations when clumps pass across the line of the sight of a distant observer. Variation timescales are estimated to be several seconds for a black hole with mass of ten to several tens of Msun, in rough agreement with the observations of some ultra-luminous X-ray sources.
Significant fraction of matter in supercritical (or super-Eddington) accretion flow is blown away by radiation force, thus forming outflows, however, the properties of such radiation-driven outflows have been poorly understood. We have performed global two-dimensional radiaion-magnetohydrodynamic simulations of supercritical accretion flow onto a black hole with 10 or 10^8 solar masses in a large simulation box of 514 r_S x 514 r_S (with r_S being the Schwarzschild radius). We confirm that uncollimated outflows with velocities of 10 percents of the speed of light emerge from the innermost part…
Indication of the Less-ionized Clumpy Ultra-Fast Outflows in Seyfert Galaxies
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency（宇宙科学研究所，日本宇宙航空研究开发机构）；Department of Astronomy, Graduate School of Science, The University of Tokyo（东京大学理学研究科天文学专攻）；Mercari；Science education research unit, University of Teacher Education Fukuoka（福冈教育大学科学教育研究单位）
Clumpy Outflows from Super-Eddington Accreting Black Holes I: Radiation Hydrodynamics Simulations and Observational Implications
Center for Computational science, University of Tsukuba（筑波大学计算科学中心）；Department of Natural Science, Faculty of Arts and Science, Komazawa University（驹泽大学文理学院自然科学系）；Department of Astronomy, Graduate School of Science, Kyoto University（京都大学理学研究科天文学系）
Supercritical accretion flows inevitably produce radiation-pressure driven outflows, which will Compton up-scatter soft photons from the underlying accretion flow, thereby making hard emission. We perform two dimensional radiation hydrodynamic simulations of supercritical accretion flows and outflows, incorporating such Compton scattering effects, and demonstrate that there appears a new hard spectral state at higher photon luminosities than that of the slim-disk state. In this state, as the photon luminosity increases, the photon index decreases and the fraction of the hard emission increases…
We solve the radiation-hydrodynamic (RHD) equations of supercritical accretion flows in the presence of radiation force and outflow by using self similar solutions. Compare with the pioneer works, in this paper we consider power-law function for mass inflow rate as $ \dot{M} \propto r^{s} $. We found that $ s = 1 $ when the radiative cooling term is included in the energy equation. Correspondingly, the effective temperature profile with respect to the radius was obtained as $ T_{\text{eff}} \varpropto r^{-1/2} $. In addition, we investigated the influence of the outflow on the dynamics of the …
We present the two-dimensional inflow-outflow solutions of radiation hydrodynamic (RHD) equations of supercritical accretion flows. Compared with prior studies, we include all components of the viscous stress tensor. We assume steady state flow and use self-similar solutions in the radial direction to solve the equations in $ r-θ$ domain of the spherical coordinates. The set of differential equations have been integrated from the rotation axis to the equatorial plane. We find that the self-similarity assumption requires that the radial profile of density is described by $ ρ(r) \propto r^{-0.5}…
We present the effects of ordered large scale magnetic field on the structure of supercritical accretion flow in the presence of outflow. In the cylindrical coordinates ($r, φ,z$), We write the 1.5 dimensional, the steady state ($\frac{\partial}{\partial t}=0$) and axisymmetric ($\frac{\partial}{\partial φ}=0$) inflow-outflow equations by using the self similar solutions. Also a model for radiation pressure supported accretion flow threaded by both toroidal and vertical components of magnetic field has been formulated. For studying the outflows, we adopt a radius dependent mass accretion rate …
Outflows are inevitably driven from the disk if the vertical component of the black hole (BH) gravity cannot resist the radiation force. We derive the mass loss rate in the outflows by solving a dynamical equation for the vertical gas motion in the disk. The structure of a supercritical accretion disk is calculated with the radial energy advection included. We find that most inflowing gas is driven into outflows if the disk is accreting at a moderate Eddington-scaled rate (up to $\sim 100$) at its outer edge, i.e., only a small fraction of gas is accreted by the BH, which is radiating at sever…
We apply our two-dimensional (2D), radially self-similar steady-state accretion flow model to the analysis of hydrodynamic simulation results of supercritical accretion flows. Self-similarity is checked and the input parameters for the model calculation, such as advective factor and heat capacity ratio, are obtained from time-averaged simulation data. Solutions of the model are then calculated and compared with the simulation results. We find that in the converged region of the simulation, excluding the part too close to the black hole, the radial distribution of azimuthal velocity $v_ϕ$, dens…
Most ultraluminous X-ray sources (ULXs) are thought to be supercritical accreting compact objects, where massive outflows are inevitable. Using the long-term monitoring data with the Swift X-ray Telescope, we identified a common feature in bright, hard ULXs: they display a quasi-periodic modulation in their hard X-ray band but not in their soft band. As a result, some sources show a bimodal distribution on the hardness intensity map. We argue that these model-independent results can be well interpreted in a picture that involves supercritical accretion with precession, where the hard X-ray emi…
Optically Thick Outflow Driven by Supercritical Accretion May Explain Little Red Dots
State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）
We study the dynamics of super-Eddington accretion flows by performing two-dimensional radiation-hydrodynamic simulations. Compared with previous works, in this paper we include the $T_{θϕ}$ component of the viscous stress and consider various values of the viscous parameter $α$. We find that when $T_{θϕ}$ is included, the rotational speed of the high-latitude flow decreases, while the density increases and decreases at the high and low latitudes, respectively. We calculate the radial profiles of inflow and outflow rates. We find that the inflow rate decreases inward, following a power law for…
We report on the long- and short-term X-ray spectral analysis of the polar-scattered Seyfert 1.2 galaxy ESO 323-G77, observed in three epochs between 2006 and 2013 with Chandra and XMM-Newton. Four high-resolution Chandra observations give us a unique opportunity to study the properties of the absorbers in detail, as well as their short time-scale (days) variability. From the rich set of absorption features seen in the Chandra data, we identify two warm absorbers with column densities and ionisations that are consistent with being constant on both short and long time-scales, suggesting that th…
We study the long-term evolution of the global structure of axisymmetric accretion flows onto a black hole (BH) at rates substantially higher than the Eddington value ($\dot{M}_{\rm Edd}$), performing two-dimensional hydrodynamical simulations with and without radiative diffusion. In the high-accretion optically-thick limit, where the radiation energy is efficiently trapped within the inflow, the accretion flow becomes adiabatic and comprises of turbulent gas in the equatorial region and strong bipolar outflows. As a result, the mass inflow rate decreases toward the center as $\dot{M}_{\rm in}…
Accretion disks of active galactic nuclei (AGN) have been proposed as promising sites for producing both (stellar-mass) compact object mergers and extreme mass ratio inspirals. Along with the disk-assisted migration/evolution process, ambient gas materials inevitably accrete onto the compact objects. The description of this process is subject to significant theoretical uncertainties in previous studies. It was commonly assumed that either an Eddington accretion rate or a Bondi accretion rate (or any rate in between) takes place, although these two rates can differ from each other by several or…
To understand why supercritical accretion is feasible onto a neutron star, we carefully examine the accretion flow dynamics by 2.5-dimensional general relativistic (GR) radiation magnetohydrodynamic (RMHD) simulations, comparing the cases of accretion onto a non-magnetized neutron star (NS) and that onto a black hole (BH). Supercritical BH accretion is relatively easy, since BH can swallow excess radiation energy, so that radiation flux can be inward in its vicinity. This mechanism can never work for NS which has a solid surface. In fact, we find that the radiation force is always outward. Ins…
In order to understand the physical processes underlying clump formation in outflow from supercritical accretion flow, we performed two-dimensional radiation hydrodynamic (RHD) simulations. We focus our discussion on the nature of RHD instability in marginally optically thick, plane-parallel, super-Eddington atmosphere. Initially we set two-layered atmosphere with a density contrast of 100 exposed to strong, upward continuum-radiation force; the lower layer is denser than the upper one, condition for an RHD instability. We assume non-zero but negligible gravitational force, compared with the r…
We present high-time resolution optical spectroscopy and imaging of the black hole transient Swift J1357.2-0933 during its 2017 outburst. The light curves show recurrent dips resembling those discovered during the 2011 outburst. The dip properties (e.g duration and depth) as well as the evolution of their recurrence time are similar to those seen in 2011. Spectra obtained during the dips are characterised by broad and blue-shifted absorptions in Balmer and He ii. The absorptions show core velocities of $\sim$ -800 km/s and terminal velocities approaching $\sim$ 3000 km/s i.e. in the upper-end …
Photon trapping and outflow are two key physics associated with the supercritical accretion flow. We investigate the conflict between these two processes based on two-dimensional radiation-hydrodynamic (RHD) simulation data and construct a simplified (radially) one-dimensional model. Mass loss due to outflow, which is not considered in the slim-disk model, will reduce surface density of the flow, and if very significant, it will totally suppress photon trapping effects. If the photon trapping is very significant, conversely, outflow will be suppressed because radiation pressure force will be r…
We present the results of a systematic, broadband X-ray spectral analysis of nearby active galactic nuclei (AGNs) with the X-ray clumpy torus model (XCLUMPY; Tanimoto et al. 2019). By adding 16 AGNs newly analyzed in this paper, we study total 28 AGNs including unabsorbed and absorbed AGNs taken from Ichikawa et al. (2015) and García-Bernete et al. (2019). This is the largest sample whose X-ray and infrared spectra are analyzed by the clumpy torus models XCLUMPY and CLUMPY (Nenkova et al. 2008), respectively. The relation between the Eddington ratio and the torus covering factor determined fro…
Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most Ultraluminous X-ray Sources (ULXs) are super-Eddington accretors of stellar mass rather than sub-Eddington intermediate mass black holes. An important prediction of theories of supercritical accretion is the existence of powerful outflows of moderately ionized gas at mildly relativistic speeds. In practice, the spectral resolution of X-ray gratings such as RGS onboard XMM-Newton is required to resolve their observational signatures in ULXs. Us…
By performing two-dimensional axisymmetric general relativistic radiation magnetohydrodynamics simulations with spin parameter $a^*$ varying from -0.9 to 0.9, we investigate the dependence on the black hole spin of the energy flow from supercritical accretion disk around stellar mass black hole. It is found that optically and geometrically thick disks form near the equatorial plane, and a part of the disk matter is launched from the disk surface in all models. The gas ejection is mainly driven by the radiative force, but magnetic force cannot be neglected, when $|a^*|$ is large. The energy out…
We present the detailed global structure of black hole accretion flows and outflows through newly performed two-dimensional radiation-magnetohydrodynamic simulations. By starting from a torus threaded with weak toroidal magnetic fields and by controlling the central density of the initial torus, rho_0, we can reproduce three distinct modes of accretion flow. In model A with the highest central density, an optically and geometrically thick supercritical accretion disk is created. The radiation force greatly exceeds the gravity above the disk surface, thereby driving a strong outflow (or jet). B…
We study the evolution of binary systems of Ultra-luminous X-ray sources and compute their optical emission assuming accretion onto a black hole via a non standard, advection-dominated slim disc with an outflow. We consider systems with black holes of $20M_{\odot}$ and $100M_{\odot}$, and donor masses between $8M_{\odot}$ and $25M_{\odot}$. Super-critical accretion has considerable effects on the optical emission. The irradiating flux in presence of an outflow remains considerably stronger than that produced by a standard disc. However, at very high accretion rates the contribution of X-ray ir…
The black-hole binary V404 Cyg entered the outburst phase in June 2015 after 26 years of X-ray quiescence, and with its behaviour broke the outburst evolution pattern typical of most black-hole binaries. We observed the entire outburst with the Swift satellite and performed time-resolved spectroscopy of its most active phase, obtaining over a thousand spectra with exposures from tens to hundreds of seconds. All the spectra can be fitted with an absorbed power law model, which most of the time required the presence of a partial covering. A blue-shifted iron-Kalpha line appears in 10% of the spe…
The origin of Ultraluminous X-ray Sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times is mysterious. The most popular models for the ULXs involve either intermediate mass black holes (IMBHs) or stellar-mass black holes accreting at super-Eddington rates. Here we review the ULX properties. Their X-ray spectra indicate a presence of hot winds in their accretion disks supposing the supercritical accretion. In recent years, new surprising results were discovered in X-ray data, ULX-pulsars and high-v…
We present simultaneous optical and near-infrared (IR) photometry of the millisecond pulsar PSR J1023+0038 during its low-mass X-ray binary phase. The r'- and K_s-band light curves show rectangular, flat-bottomed dips, similar to the X-ray mode-switching (active-passive state transitions) behaviour observed previously. The cross-correlation function (CCF) of the optical and near-IR data reveals a strong, broad negative anti-correlation at negative lags, a broad positive correlation at positive lags, with a strong, positive narrow correlation superimposed. The shape of the CCF resembles the CCF…
Highly accreting quasars are quite luminous in the X-ray and optical regimes. While, they tend to become radio quiet and have optically thin radio spectra. Among the known quasars, IRAS F11119+3257 is a supercritical accretion source because it has a bolometric luminosity above the Eddington limit and extremely powerful X-ray outflows. To probe its radio structure, we investigated its radio spectrum between 0.15 and 96.15 GHz and performed very-long-baseline interferometric (VLBI) observations with the European VLBI Network (EVN) at 1.66 and 4.93 GHz. The deep EVN image at 1.66 GHz shows a two…
We examine optical V-band light curves in luminous eclipsing black hole X-ray binaries, using a supercritical accretion/outflow model that is more realistic than the formerly used ones. In order to compute the theoretical light curve in the binary system, we do not only apply the global analytic solution of the disk, but also include the effect of the optically thick outflow. We found that the depth of eclipse of the companion star by the disk changes dramatically when including the effect of the outflow. Due to the effect of outflow, we can reproduce the optical light curve for typical binary…
We present the ionised gas outflow morphology in the Circinus galaxy using the Narrow Field Mode (NFM) of the MUSE instrument on board the Very Large Telescope (VLT). The NFM observations provide a spatial resolution of $\sim$0.1", corresponding to a physical scale of $\sim$2 pc, one of the highest spatial resolution achievable using ground-based AO-assisted observations in the optical wavelengths. The MUSE observations reveal a collimated clumpy outflow profile originating near the AGN location and extending up to 1.5" ($\sim$30 pc) in the NW direction. The collimated structure then fragments…
The nature of ultraluminous X-ray sources (ULXs) -- off-nuclear extra-galactic sources with luminosity, assumed isotropic, $\gtrsim 10^{39}$ erg s$^{-1}$ -- is still debated. One possibility is that ULXs are stellar black holes accreting beyond the Eddington limit. This view has been recently reinforced by the discovery of ultrafast outflows at $\sim 0.1$-$0.2c$ in the high resolution spectra of a handful of ULXs, as predicted by models of supercritical accretion discs. Under the assumption that ULXs are powered by super-Eddington accretion onto black holes, we use the properties of the observ…
Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution X-ray and UV observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas never seen before. It blocks 90% of the soft X-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to fiv…
We present evidence for the rapid variability of the high velocity iron K-shell absorption in the nearby ($z=0.184$) quasar PDS456. From a recent long Suzaku observation in 2013 ($\sim1$Ms effective duration) we find that the the equivalent width of iron K absorption increases by a factor of $\sim5$ during the observation, increasing from $<105$eV within the first 100ks of the observation, towards a maximum depth of $\sim500$eV near the end. The implied outflow velocity of $\sim0.25$c is consistent with that claimed from earlier (2007, 2011) Suzaku observations. The absorption varies on time-s…
Dissecting the Nuclear Structure of NGC 5548 with XRISM. I. Physical Properties of the Highly Ionized Outflows
University of Michigan（密歇根大学）；SRON Netherlands Institute for Space Research（荷兰空间研究所）；Leiden University（莱顿大学）；Space Telescope Science Institute（太空望远镜科学研究所）；James Madison University（詹姆斯·麦迪逊大学）；Technion（以色列理工学院）
It has recently been discovered that a fraction of ultra-luminous X-ray sources (ULXs) exhibit X-ray pulsations, and are therefore powered by super-Eddington accretion onto magnetized neutron stars (NSs). For typical ULX mass accretion rates ($\gtrsim 10^{19}\,{\rm g\,s^{-1}}$), the inner parts of the accretion disc are expected to be in the supercritical regime, meaning that some material is lost in a wind launched from the disc surface, while the rest forms an optically thick envelope around the NS as it follows magnetic field lines from the inner disc radius to the magnetic poles of the sta…
