1 / 26

Accretion onto Black Hole : Advection Dominated Flow

Accretion onto Black Hole : Advection Dominated Flow. K. Hayashida Osaka University. Free Fall & Escape Velocity. E=0 (at Infinite) E=1/2v 2 -GM/r=0 (at r ) v=sqrt(2GM/r) v=Free Fall Velocity=Escape Velocity v=c … r=r g =2GM/c 2 Schwartzshild radius

gina
Télécharger la présentation

Accretion onto Black Hole : Advection Dominated Flow

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Accretion onto Black Hole : Advection Dominated Flow K. Hayashida Osaka University

  2. Free Fall & Escape Velocity • E=0 (at Infinite) • E=1/2v2-GM/r=0 (at r ) • v=sqrt(2GM/r) • v=Free Fall Velocity=Escape Velocity • v=c … r=rg =2GM/c2 Schwartzshild radius • 3km for 1Mo

  3. Kepler Motion • GM/r2 = v2/r = rW2 • v=sqrt(GM/r) ; W =sqrt(GM/r3) • l (angular momentum) = vr = sqrt(GMr) • E=1/2 v2 –GM/r = –GM/2r = –(GM)2/2l2 • To accrete from r1 to r2, particle must lose DE=GM/2r2 – GM/2r1 … e.g. Radiation • Must lose Dl=sqrt(GMr1) - sqrt(GMr2) …Angular Momentum Transfer

  4. Angular Momemtum Flow Viscosity v(r) r • Viscosity force • h: dynamical viscotiy • h =rn (n: kinematic viscosity) • ※Viscosity time scale >Hubble time unless　turbulence or magnetic field exists. r-Dr v(r-Dr)

  5. Effective Potential • Stable Circular Orbit r>=3rg • Binding Energy at r=3rg =0.0572c2 • … Mass conversion efficiency

  6. Accretion Flow (Disk) Models • Start from Kepler Motion • Optically Thick Standard Disk • Optically Thin Disk • Irradiation Effect, Relativistic Correction, Advection etc. • Slim Disk (Optically Thick ADAF) • Optically Thin ADAF • Start from Free Fall • Hydrodynamic Spherical Accretion Flow=Bondi Accretion … transonic flow

  7. Standard Accretion Disk Model • Shakura and Sunyaev (1973) • Optically Thick • Geometrically Thin (r/H<<1) • Rotation = Local Keplerian • Steady, Axisymmetric • Viscosity is proportional to Pressure

  8. Standard Disk Model-2 • Mass Conservation • Angular Velocity • Angular Momentum Conservation • Hydrostatic Balance One zone approx.

  9. Standard Disk Model-3 • Energy Balance • Equation of State • Opacity • Viscosity Prescription a-disk model

  10. Standard Disk Thermal Equilibrium Curve Corresponds to L~0.1LEdd • Double Valued Solutions for fixed S

  11. Standard Disk Heating and Cooling • Low Temperature • High Temperature

  12. Disk Blackbody Spectra • Total Disk (see Mitsuda et al., 1984)

  13. Optically Thin Disk • Problem of Optically Thick Disk • Fail to explain Hard X-ray, Gamma-ray Emission • Optically Thin Disk (Shapiro-Lightman-Earley Disk) (1976) • Radiation Temperature can reach Tvir

  14. Optically Thin Disk-2 • Energy Balance • Disk

  15. Stability (Secular, Thermal)

  16. Advection Terms • Energy Equation • Energy Balance

  17. Optically Thick (& High dM/dt) ADAF ADAF

  18. Optically Thin (& Low Density) ADAF • Depending on S, Number of Solutions Changes.

  19. Thermal Equilibrium ADAF (Optically Thin)

  20. Thermal Equilibrium ADAF ADAF (thick or thin)… H/r ~1 Conical Flow

  21. ADAF (Opticallt Thick and Thin)

  22. Optically Thin, Two Temperature ADAF

  23. dM/dt is known from observation. L is too low unless ADAF is considered. Optically Thin, Two Temperature ADAF (Model fit to SgrA)

  24. Presence of Event Horizon : BH vs NS • Luminosity at Quiescence Lmin • NS with Surface • BH without Surface Narayan et al., Theory of Black Hole Accretion Discs, 1998, p.177

  25. NLS1 Slim　Disk　Model = Optically Thick ADAF Mineshige et al., 2000

  26. Summary

More Related