1. STScI Workshop on Massive Stars 8 - 11 May 2006 Baltimore Multiplicity of Massive Stars - Clues and Consequences Hans Zinnecker (AIP, Potsdam, Germany)

2. goal of this short contribution -remind you of high incidence of binaries, triples, and Trapezium systems - remind you of preponderance of close massive binaries (SB2, SB1, eclipsing binaries) - new idea to explain the origin of Trapezium systems - new idea to explain the origin of the close binaries

3. goal of this short contribution (ctd.) - Example:The Orion Trapezium Cluster (origin and future evolution) - Question: seperations and mass ratios for massive close binaries to become `` interactive´´? (case A, B, C mass transfer) RLOF:mass / A.M. accretion efficiency? LBV:violent mass loss (stellar wind), onset at which initial stellar mass? stellar rejuvenation? population synthesis!

4. HST image 1’’ 0.5’’ B2 B3 B4 B1 sep = 38 mas 0.05’’ * * C2 C1 0.1’’ A2 A1 sep = 215 mas  B2-3: sep = 117 mas 1997.8 2001.2 10 AU 1999.1 1998.8 High-resolution infrared speckle reconstruction 2003.8 Schertl et al. (2003, A&A) Young, massive Orion Trapezium multiples: orbital motion, stellar masses, & ages

5. other relevant considerations (not today) - formation clues from observed multiplicity trends in different stellar environments - consequences of multiplicities for runaways, non-local supernovae, starburst population synthesis including exotic products of binary stellar evolution (high mass X-ray binaries, binary pulsars, TZ-objects)

6. outline of this talk -quick summary of multiplicity observations for massive stars (spectroscopic, speckle, adaptive optics, HST/FGS observations) -example: the multiplicities of the Orion Trapezium stars and the companion star frequency of high-mass vs. low-mass stars -SPH simulations: hierarchical star cluster formation and the merging of subclusters as a model for the origin of Trapezia -origin due to formation or early dynamical N-body evolution (accretion onto low-mass binary, hardening of a wide-binary)

7. outline of another talk (not today) -massive binaries in different stellar environments: young clusters rich and poor, OB associations, runaway stars -stellar evolution of massive tight binaries (RLOF; mergers) high-mass X-ray binaries, supernova kicks, gamma-ray bursts

8. Some References - Bonnell and Bate (2005): MNRAS 362, 915 - Langer et al. (2003), IAU-Symp. 212 - Mason et al. (1998), AJ 115, 821 - Mermilliod/Garcia (2001), IAU-Symp. 200 - Petrovic et al. (2005), A&A 435, 1013 - Portegies Zwart (2001), IAU-Symp. 200 - Preibisch et al (2001), IAU-Symp. 200 - Van Bever & Vanbeveren (1998), A&A 334, 21 - Zinnecker (2003), IAU-Symp. 212 - Zinnecker (2006): Sacacomie Proc. - Zinnecker (2006): Tartu Proc. - Zinnecker (2006): ESO Workshop Proc.

9. García, B. & Mermilliod, J. C. 2001, A&A 368, 122

10. Brown, A. G. A. 2001, AN 322, 43

11. A Trapezium system in M16? McCaughrean, M. J. & Andersen, M. 2002, A&A 389, 513

12. HST image 1’’ 0.5’’ B2 B3 B4 B1 sep = 38 mas 0.05’’ * * C2 C1 0.1’’ A2 A1 sep = 215 mas  B2-3: sep = 117 mas 1997.8 2001.2 10 AU 1999.1 1998.8 High-resolution infrared speckle reconstruction 2003.8 Schertl et al. (2003, A&A) Young, massive Orion Trapezium multiples: orbital motion, stellar masses, & ages

13. Definition ``massive´´ (primary) stellar mass M * > 10 solar masses spectral type earlier than B2 main sequence lifetime < 10 Myr Definition ``multiplicity´´ binaries (EB, SB, VB) hierarchical triples / quadruples Trapezium-type systems

14. Definition ``Multiplicity´´ or companion star fraction (csf) Reipurth & Zinnecker 1993, A&A 278, 81 e.g.csf = 1.5for Trapezium stars * 1 single *.1double *..1 triple *. :1 quadruple PS.csf = 0.5for low-mass stars (T Tauri stars) in Orion Nebula Cluster

15. Origin of the Trapezium Cluster via hierarchical merging of subclusters Bonnell, I. A.; Bate, M. R.; & Vine, St. G. 2003, MNRAS 343, 413 SPH simulations of a 1000 M sun turbulent mol. cloud

17. dynamical and binary stellar evolution of the Trapezium Cluster (next 30 Myr) dynamical ejections of massive stars (cf. AE Aurigae and  Columbae) close binary evolution of massive stars (future of Theta-1 Ori C, A, B binaries?)

18. Hoogerwerf, R.; de Bruijne, J. H. J.; de Zeeuw, P. T. 2001, A&A 365, 49

19. Origin of close binary systems (Bonnell & Bate 2005) Idea: wide low-mass binary mass + A.M. accretion close high-mass binary

20. Origin of close binary systems Another (older) idea: shrinking (hardening) of wide high-mass binary systems by close stellar encounters in dense clusters (energy exchange in multiple systems)

21. Future stellar evolution of the close binaries in the Orion Trapezium Cluster Case A mass transfer: P ~ 10 d Case B mass transfer: P ~ 100 d Case C mass transfer: P ~ 1000 d WR/O-stars, RSG, SN II, HMXB?

22. Theta-1-A 16 + 2 Msun, sep = 1 AU Theta-1-B 7 + 3 Msun, sep = 0.13AU Theta-1_C 40 + 5 Msun, sep = 16 AU Theta-2-A 25 + 8 Msun, sep = 0.5 AU Nu Ori 14 + 3 Msun, sep = 0.35AU Iota Ori 21 + 17 Msun, sep =? Ecc.!

23. Other observational results for other young star clusters: S255-IR, NGC3603, R136,...

25. Zinnecker, Correia, Stecklum et al. 2005, in prep.

26. Stolte, A.; Brandner, W.; Brandl, B.; Zinnecker, H.; Grebel, E. K. 2004, AJ 128, 765

27. Stolte, A.; Brandner, W.; Brandl, B.; Zinnecker, H.; Grebel, E. K. 2004, AJ 128, 765

28. Moffat, A. F. J.; Drissen, L.; Shara, M. M. 1994, ApJ 436, 183

29. Hofmann, K.-H. & Weigelt, G. 1986, A&A 167, L15

30. Weigelt, G.; Baier, G. 1985,Massey, Ph.; Hunter, D. A. 1998, A&A 150, L18 ApJ 493, 180

31. Massey, Ph.; Penny, L. R.; Vukovich, J. 2002, ApJ 565, 982

32. Apai, D.; Bik, A.; Kaper, L.; Henning, Th.; Zinnecker, H. in prep.

33. Bosch, G.; Selman, F.; Melnick, J.; Terlevich, R. 2001, A&A 380, 137

34. Conclusions --------------- 1)Some of the most exciting cosmic phenemena due to the presence of massive close binaries 2) Studies of star forming regions & young clusters allow us to observe binary parameter distributions give extra info on massive star formation provide I.C. for models of interacting binary evol 3) We all need to learn more about binary evolution! 4) Orion and other nearby clusters as starting point

35. Conclusions (ctd.) 4) Dynamical interactions also important (ejections, runaway stars) and generally underestimated… 5) Orion Trapezium cluster and other nearby young clusters as a starting point (link I.C. to evolutionary consequences) PS. Watch out for ARAA review on massive star formation in preparation by YORKE & ZINNECKER 2007

36. consequences a) implications of high-mass multiplicity derive stellar masses (eclipsing SB2) correct upper IMF slope (steepening) correct cluster vel. dispersion (dyn. mass) origin of runaway OB stars (ejection) high-mass X-ray binaries (stellar mass BH) colliding winds, orbital drag & decay effect on WR & SN-II progenitor masses distance determination using eclipsing SB2

37. consequences b) questions related to multiplicity very massive stars (M > 100 Mo) through binary mergers? multiplicity of isolated massive stars in the field? multiplicity and stellar rotation of the components? multiplicity in low-metallicity environments (LMC / SMC)?

38. multiplicity among massive stars M > 8 M  SpT earlier B2 conclusions: 1)Trapezia within Orion Trapezium 2)preponderance of tight binaries SB1: q  1lower masses SB2: q = 1higher masses 3)20 out of 25 O-stars are triple, consisting of SB + VB pairs (Mason) 4)multiplicity among massive stars higher than among low-mass (3x) WHY?  gravitational dynamics