1. Transient torus A unified after-AGB binary scenario? A.Frankowski Institut d’Astronomie et d’Astrophysique, ULB, Brussels, Belgium

2. 1. 1.The family of “after AGB” binaries 2. 2.The binary evolution channels 3. 3.Dynamical RLOF versus wind accretion : no period gap: a 20-yrs old problem! eccentric orbits at short periods 4. 4.New observational hints: rapid rotation of the accreting companions circumbinary disks 5. 5.Quest for a binary channel avoiding the period gap SUMMARY

3. 1.The family of “after AGB” binary systems…...all binaries in which at least one component has gone through the AGB binary evolution scheme

4. 1.The family of “after AGB” binary systems…...includes several classes of s-process-rich stars resulting from mass transfer from a former AGB companion (now a white dwarf) after AGB ≠ post-AGB!

5. 1.The family of “after-AGB” binary systems… …is not confined to s-process-rich objects! 1.Post-AGB stars (some s-process-rich, not all!) Dominik et al. A&A 397, 595-609 (2003)

6. 1.The family of “after-AGB” binary systems… …is not confined to s-process-rich objects! 2.Binary CSPNe 1.Post-AGB stars (some s-process-rich, not all!) ionising UV

7. 1.The family of “after-AGB” binary systems… 3.Red symbiotics with massive WD companions (M h > 0.5M sun ) …is not confined to s-process-rich objects! 1.Post-AGB stars (some s-process-rich, not all!) Tomov, 1995, MNRAS, 272, 189 2.Binary CSPNe

8. 1.The family of “after-AGB” binary systems… …is not confined to s-process-rich objects! 4.Cataclysmic variables (some “after AGB”, not all!) 1.Post-AGB stars (some s-process-rich, not all!) 2.Binary CSPNe 3.Red symbiotics with massive WD companions (M h > 0.5M sun )

9. 1.The family of “after-AGB” binary systems… 3.Red symbiotics with massive WD companions (M h > 0.5M sun ) …is not confined to s-process-rich objects! Why some “after AGB” stars show peculiar abundances while others do not? Partially solved, with the exception of: why not all post-AGB are s-process-rich? why red symbiotics are not S stars? 2.Binary CSPNe 4.Cataclysmic variables (some “after AGB”, not all!) 1.Post-AGB stars (some s-process-rich, not all!) Frankowski & Jorissen 2007, BaltAstr 16, 104

10. 1.The family of “after-AGB” binary systems… 3.Red symbiotics with massive WD companions (M h > 0.5M sun ) …is not confined to s-process-rich objects! Do we understand their orbital characteristics? 2.Binary CSPNe 4.Cataclysmic variables (some “after AGB”, not all!) 1.Post-AGB stars (some s-process-rich, not all!)

11. 2. Binary evolution channels tidal interactions wind accretion, tidally enhanced wind Roche-lobe overflow common envelope event

12. 2. Binary evolution channels Jorissen, 2003, AGB stars, Springer Fundamental Mira pulsation period (d) Orbital period (d)

13. 2. Binary evolution channels Catastrophic outcome generally associated with mass transfer through RLOF from the more massive AGB star with a deep convective envelope After O. Pols, 2005

14. 3. Hard reality (or dynamical RLOF versus wind accretion) Frankowski, Ph.D. thesis, 2004 Post-AGB S Ba (triple) Ba S (large f[M])

15. Solutions proposed thus far How to avoid drastic CE orbit shrinkage: CRAP (Companion-Reinforced Attrition Process) Tout & Eggleton 1988, MNRAS 231, 823 inhibits s-process pollution Diminished binding energy of the envelope Han et al. 1995, MNRAS 277, 1442 Dewi & Tauris 2000, A&A 360, 1043 is ionisation energy recyclable? Inclusion of tidal forces Karakas et al. 2000, MNRAS, 316, 689; Pols et al. 2003, in: Symbiotic stars probing stellar evolution, ASP Conf. Ser. 303, p. 293 did not help Angular-momentum-balance-based CE instead of energy-based Nelemans et al. 2000, A&A 360, 1011; Nelemans & Tout 2005, MNRAS 356, 753 what physics?

16. Solutions proposed thus far Eccentricity pumping by a circumbinary disk Waelkens et al. 1996, A&A 314, L17 Artymowicz et al. 1991, ApJ 370, L35 but: only for detached systems! How to stay eccentric: Dwarf Ba Post-AGB Ba Periastron mass loss Soker, 2000, A&A 357, 557

17. 4. Observational hints 56 Peg Frankowski & Jorissen 2006, Observatory 126, 25 HD 165141 Jorissen et al. 1996, A&A 306, 467 d’ symbiotics Jorissen et al. 2005, A&A 441, 1135 WIRRing stars Jeffries & Stevens 1996, MNRAS 279, 180 Abell-35 CSPNe Thevenin & Jasniewicz 1997, A&A 320, 91 = Evidence for fast rotation, due to spin accretion from wind Theuns et al. 1996, MNRAS 280, 1264 4.1 RS CVn and Ba (seemingly conflicting) properties in the same object: - long orbital periods typical of Ba/symbio - X-rays, Halpha emission typical of RS CVn - fast rotation

18. 4. Observational hints Bipolar PNe (also some ellipticals) the reason we are here V Hya (S) Knapp et al. 1999, A&A 351, 97  Gru (S) Sahai 1992, A&A 253, L33 Post-AGBs Van Winckel 2003, ARA&A 41, 391 … 4.2 Circumbinary disks/waists/toruses, bipolar outflows: Dominik et al. A&A 397, 595-609 (2003)

19. 4. Observational hints 4.3 New results on binarity of early M giants from CORAVEL/ELODIE campaign to monitor RV of Hipparcos survey stars Jorissen et al. 2007, in preparation binarity rate of ~15% e-log P diagram! Early M giant binaries share the tidal envelope of post-AGBs... do they just stay in place!?

20. 4. Observational hints (stressed by theoreticians!) Reshaping of the Roche equipotentials Reduction of the effective gravity of the mass-losing star Jorissen 2003, AGB Stars, Springer, 461 Schuerman 1972, ApSS 19, 351 4.3 Pulsation, dust formation and radiation-driven wind: Frankowski & Tylenda 2001, A&A 367, 513

21. 4. Theoretical hints 4.4 Role of a non-catastrophic RLOF mass transfer despite a deep convective envelope when the companion is massive enough (depleting the convective envelope eases the condition somewhat) Hjellming & Webbink 1987, ApJ 318, 794 possibility of L 2 /L 3 outflows e.g. Podsiadlowski, Joss & Hsu 1992, ApJ 391, 246

22. 5. The ‘transient torus’ scenario - avoiding the period gap Wind accretion an accretion disc is formed the companion is spun-up efficiently (Near) RLOF with substantial L 2 /L 3 dusty outflows importance of wind acceleration zone

23. 5. The ‘transient torus’ scenario - avoiding the period gap Formation of a Keplerian disk from torus' leftovers pumping up the eccentricity Formation of a circumbinary torus radiation pressure acts on dust matter escapes through the vicinity of the outer Lagrangian point Fallback due to shadowing?

24. 5. The ‘transient torus’ scenario - tidal effects of the circumbinary disk The most simplistic approach to the binary-disk tidal interaction – slowing down the stars at apastron. Phase lag required for tidal operation, so: v ap >V disk This leads to a limiting eccentricity of about 0.5-0.6. Disk mass ~10 -2 M ⊙ enough for getting high eccentricities.

25. 5. The 'transient torus' - the effect on the e-log P diagram Placing the simple e limit on the e-log P diagrams of after-AGB systems looks very promising! Closer check: assume that this disk evolution follows the L2 outflow stage and proceeds until the disk is pushed to a certain distance.

26. Post-AGB S Ba (triple) Ba S (large f[M]) 5. The ‘transient torus’ scenario - at work

27. 1. Finally something that resembles the observed e-log P diagram for post-AGB, Ba and related stars! 2. s-process enriched and non-enriched post-AGBs are naturally mixed, depending on the TT timing and mass of the companion 3. Smaller eccentricities of Ba stars possibly due to a combination of primary's evolutionary stage at TT, mass of the secondary and tidal effects at secondary's ascent to RGB

28. Summary 1. Attempt to understand the after-AGB binaries together, as sharing defining moments in life. 2. Various observational and theoretical hints led us to formulation of the 'transient torus' scenario. 3. Promising first results for the e-log P diagram of post-AGB, Ba and S stars!