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Accretion discs: models vs reality

Accretion discs: models vs reality. Jean-Pierre Lasota. Institut d’Astrophysique de Paris. Jean-Alain Marck. Dwarf novae. SS Cyg. Cataclysmic Binary Stars. red dwarf. “hot spot”. accretion disc. white dwarf. Discs (in CVs) are: Keplerian

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Accretion discs: models vs reality

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  1. Accretion discs: models vs reality Jean-Pierre Lasota Institut d’Astrophysique de Paris

  2. Jean-Alain Marck

  3. Dwarf novae SS Cyg

  4. Cataclysmic Binary Stars red dwarf “hot spot” accretion disc white dwarf

  5. Discs (in CVs) are: • Keplerian • geometrically thin (but not “infinitely” thin) • not always in equilibrium (thermal and/or viscous) • (almost ?) flat • non-adiabatic (radiate like hell !) • not always (?) axisymmetric • non-selfgravitating • jetless !

  6. Smak 1994

  7. Webb et al. 1999

  8. Doppler tomography: 2D Steeghs 2001

  9. Steeghs 2001

  10. Steeghs 2001

  11. Steeghs 2001

  12. MODELS De Villiers et al. 2004 ? Balbus 2005

  13. Radial For subsonic turbulence equivalent to b prescription (Duschl et al 2000)

  14. Vertical

  15. Q+ = Q-

  16. Local limit-cycle quiescence Menou, Hameury, Stehle 1998

  17. Hameury et al.1998

  18. Dubus 2001

  19. Buat-Ménard et al. 2001

  20. * * Smak 2000

  21. Hameury 2001

  22. new old Hameury 2001

  23. Proposed solution (Gammie & Menou 1997) Cannot work: there is accretion during quiecence !

  24. Accretion stream

  25. Maybe it is not turbulence ?

  26. Superoutbursts Superhumps VW Hyi V436 Cen (Semeniuk 1980) (AAVSO)

  27. “Standard model”: superhumps due to tidal, eccentric instability. (3:1 eccentric inner Lindblad resonance; Lubow 1991) Condition: Murray & Armitage 1998 Osaki: Superoutbursts due to a tidal-thermal instability

  28. Fully radiative Isothermal Kornet & Rożyczka (1998)

  29. Superoutburst in U Gem Superhumps in U Gem !(Smak 2005)

  30. TV Col …and in any case no need for tidal-thermal instability in LMXB outbursts

  31. Conclusions • CVs are the best systems for studying accretion discs • Observations will bring a tremendous amount of data on disc structure • There are (at least) two kinds of “viscosity” • Numerical simulations will play an important role but thinking should not be abandoned • The role of tidal forces has to be re-examined • 3D is essential but without radiative cooling included it might be of little relevance

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