Global Magnetohydrodynamic Simulations of State Transitions in Black Hole Candidates Ryoji Matsumoto (Chiba Univ.) Collaborators: Takayuki Ogawa, Tomohisa Kawashima (Chiba Univ.) Hiroshi Oda (Shanghai Obs.), and Mami Machida (Kyushu Univ.) 4 th International MAXI Workshop Nov. 30 – Dec. 2, 2010

Activities of Black Hole Candidates Makita and Matsuda X-ray light curve of Cyg X-1 (Negoro 1995) Microquasar GRS AGN Jets (NGC4261) SS433 Jet Mirabel and Rodriguez 1998

Magnetic Activities of Accretion Disks 3 Magnetic fields play essential roles in the angular momentum transport which enables the accretion and release of the gravitational energy

Magneto-rotational Instability MRI Angular momentum Balbus and Hawley (1991), Velikhov (1959)

Three-dimensional Global MHD Simulations of Black Hole Accretion Disks Initial state t=26350 unit time t 0 =rg/c Machida and Matsumoto 2003

Outflows from Accretion Disks 6

7 Structure of the Launching Region of the Outflow Isosurface of vz=0.05c Magnetic field lines and azimuthal magnetic field Machida and Matsumoto 2008

How a Black Hole Looks Like

State Transitions in Black Hole Candidates

State Transitions Observed in XTE J Nakahira et al MAXI Science News #17 1/21 Jet ejection

Evolution of Outbursts in Hardness-Intensity Diagram Remillard 2005 Hard state KeV Soft state KeV Optically thick cold disk Optically thin hot disk XTE J

Classical Accretion Disk Models give too Low Transition Luminosity Solid Curves : Thermal Equilibrium Curves (Abramowicz et al. 1995)

Three-Dimensional MHD Simulation including Optically Thin Cooling Radiative Cooling : Qrad = Q b T 1/2 density temperatureToroidal field Machida et al. 2006, PASJ 58, 193

14 Time Evolution β=P gas /P mag

15 Formation of a Magnetically Supported Disk Before the transitionAfter the transition Machida, Nakamura and Matsumoto 2006

16 Schematic Picture of the Growth of the Cooling Instability Cool Down Optically Thin Hot Disk Supported by Gas Pressure Radiative Cooling ~ 10 Optically Thin Cool Disk Supported by Magnetic Pressure < 1 Final state after the onset of the cooling instability depends on the total azimuthal magnetic flux

Thermal Equilibrium Curves including Azimuthal Magnetic Fields Oda et al. 2009

Evolution of an Accretion Disk Steady Model Oda et al XTE J Nakahira et al. 2010)

Development of Next Generation MHD Simulator for Accretion Disks Simulation Engine Platform of MHD Simulator : CANS Simulation Examples Simulation Analysis Radiation MHD Web PageVisualization Optimization for Parallel Computers Riemann Solvers Relativistic MHD Application to Accretion Disks Time Variation of RIAF Hard to Soft State Transition Evolution of Soft/Slim Disks Formation of Relativistic Jets

From HD/MHD to Radiation MHD HD 3D MHD Radiation MHD N 6 ×N step + (t,x,y,z ) Cost N 3 ×N step ρ(t,x,y,z), v(t,x,y,z), P(t,x,y,z) +B(t,x,y,z) Solve Radiation Transfer 3D Mesh Finite Difference Flux Limited Diffusion

Basic Equations Interaction with radiation

Global Radiation MHD Simulation Takeuchi, Ohsuga, and Mineshige 2010 SS433 Axisymmetric 2D Radiation MHD Simulation We are extending this simulation to 3D Radiation MHD

Accretion Disk Dynamos and Quasi-Periodic Oscillations X-ray Image by HINODE Satellite Butterfly Diagram of Sunspots (NASA) Optical image of sunspots by HINODE

Quasi-Periodic Oscillations s in Black Hole Candidates Power Density Hz GX Hz XTE J McClintock and Remillard 2004

Local 3D MHD Simulation (Shi, Krolik, and Hirose 2010) 25 Time Variation of Azimuthal Magnetic Fields White β Black dln|B|/dz < 0 Quasi periodic reversal in time scale of 10 rotation

How Azimuthal Magnetic Field Reverses ? Growth of MRI Buoyant escape of magnetic flux Buoyant rise MRI Parker Instability

QPOs Appear during the Hard-to-Soft Transition QPOs Solid Curves : Thermal Equilibrium Curves (Abramowicz et al. 1995)

High temperature(HT) model Low temperature (LT) model Formation of an Inner Torus and QPOs for Cool Accretion Flow Formation of the inner torus is essential for QPOs Machida and Matsumoto 2008 Low frequency QPO QPO period is about 10 rotation of the inner torus

Radial Distribution of Oscillation Model HT Model LT Machida et al. 2008

Summary Global 3D MHD simulations enabled us to study the evolution of an accretion disk without assuming the alpha-viscosity During the hard-to-soft transition, magnetically supported, cool disk is formed. This disk can explain the luminous hard state observed in black hole candidates Global 3D Radiation MHD simulations will reveal the mechanism of transitions to the soft state Disk dynamo can generate low frequency QPOs

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