Ecology of Blue Stragglers: Closing Thoughts and Discussion

1. Ecology of Blue Stragglers:Closing Thoughtsand Discussion

2. “Two Perspectives are Better than One” MicroEconomics MicroAstronomics MacroEconomics MacroAstronomics Bimodal radial distributions Dual CMD sequences Dalessandro Lanzoni Kudos to Ferraro et al. for making data available!

3. MicroAstronomics MacroAstronomics Bimodal radial distributions Dual CMD sequences Dependence on environment (N vsr) No dependence on collision rate Dependence of FBSS on fbin, photo Santana Knigge

4. MicroAstronomics MacroAstronomics Bimodal radial distributions Dual CMD sequences No dependence on collision rate No dependence on collision rate Dependence on Mcore, fbin Dependence on Mcore, fbin Dependence on environment (N vsr) Dependence on environment (N vsr) Population synthesis Population synthesis Cluster dynamical modeling Cluster dynamical modeling McMillan Perets Kudos to Ahumada for catalogs Chen Kudos to Davies!

5. MicroAstronomics MacroAstronomics Bimodal radial distributions Binary frequencies Binary period distributions Dual CMD sequences Binary secondary stars No dependence on collision rate Dependence on Mcore, fbin Dependence on environment (N vsr) Population synthesis Cluster dynamical modeling Geller 

6. All of the preceding: High binary fraction Deficit of short (and very long) periods Low orbital eccentricities Small mass functions No visible secondaries tell us that FBS are a species sui generis Preston (Field) • Hard binary frequency 76% • Typical orbital period ≈ 1000 days • Typical secondary mass 0.5 Mo • Lower orbital eccentricities • All SB1 Mathieu (NGC 188)

7. MicroAstronomics MacroAstronomics Bimodal radial distributions Binary frequencies Binary period distributions Dual CMD sequences Binary secondary stars No dependence on collision rate Modestly rapidly rotating Dependence on Mcore, fbin Dependence on environment (N vsr) Population synthesis Cluster dynamical modeling Lovisi

8. 1.07 d S1082 MicroAstronomics MacroAstronomics Bimodal radial distributions Binary frequencies Binary period distributions Dual CMD sequences Binary secondary stars No dependence on collision rate 2.52 Mo Modestly rapidly rotating Dependence on Mcore, fbin Early chemical abundances Dependence on environment (N vsr) Early mass measurements Population synthesis 1.58 Mo Cluster dynamical modeling Mucciarelli

9. Sills MicroAstronomics MacroAstronomics Bimodal radial distributions Binary frequencies Binary period distributions Dual CMD sequences Binary secondary stars No dependence on collision rate Modestly rapidly rotating Dependence on Mcore, fbin Early chemical abundances Dependence on environment (N vsr) Early mass measurements Population synthesis Evolutionary tracks Cluster dynamical modeling Mass transfer modeling Ivanova

10. “Two Perspectives are Better than One” MicroAstronomics MacroAstronomics Bimodal radial distributions Binary frequencies Binary period distributions Dual CMD sequences Binary secondary stars No dependence on collision rate Modestly rapidly rotating Dependence on Mcore, fbin Early chemical abundances Dependence on environment (N vsr) Early mass measurements Population synthesis Evolutionary tracks Cluster dynamical modeling Mass transfer modeling

11. Outstanding Questions In light of this workshop, what should be the definition of a blue straggler? ( but only if you are “under 40”! ) ( or over 70 – George Preston gets last word! )

12. Outstanding Questions What is the CMD telling us? Do we understand CMD locations of BS? Should we believe anything from (standard) evolution theory? Dynamical 1.5 Mo Alison – “I don’t understand how to get such low luminosities.” Natasha – “I don’t understand how to get those masses.” Photometric x

13. Outstanding Questions What is the CMD telling us? Do we understand CMD locations of BS? Should we believe anything from (standard) evolution theory? Should we believe anything from population synthesis? And therefore “kitchen sink” models?

14. Outstanding Questions Leigh, Knigge, Sills, Perets, Sarajedini & Glebbeek (2012) What is the CMD telling us? Do stellar collisions occur?

15. Outstanding Questions What is the CMD telling us? Do stellar collisions occur? What are the products? Where are the products? Superb work has been done at the macro level - Now the work needs to be done at the micro level, both observation and theory. In both globular clusters and open clusters … Abundances, rotation, masses, binarity, companions Leigh & Sills 2011

16. Outstanding Questions 7 Gyr What is the CMD telling us? Do stellar collisions occur? What can we learn from angular momentum? What are we missing by not considering magnetic fields? 2.5 Gyr

17. Outstanding Questions What is the CMD telling us? Do stellar collisions occur? What can we learn from angular momentum? What are we missing by not considering magnetic fields? What can we learn from chemical abundances? Is there hope of microastronomic diagnostics of formation? Need to learn more from George P. about s-process abundances!

18. Outstanding Questions What is the CMD telling us? Do stellar collisions occur? What can we learn from angular momentum? What are we missing by not considering magnetic fields? What can we learn from chemical abundances? What can we learned from evolved populations? Possible indirect handle on masses

19. Outstanding Questions What is the CMD telling us? Do stellar collisions occur? What can we learn from angular momentum? What are we missing by not considering magnetic fields? What can we learn from chemical abundances? What can we learned from evolved populations? Possible indirect handle on masses Are there circumstellar diagnostics for any of these processes? Has anyone looked?

20. How Shall We Move Forward? Wisconsin Badger

21. “Clean Up (Y)our Language!” “Binary” as in “Binary Frequency” as in “Close Binary” binary Mathieu Davies Chen as in “Consistent with binary formation channel”

22. “Clean Up (Y)our Language!” Mass Transfer As in “Consistent with mass transfer origin” Roche Lobe Overflow Case A Case B Case C Wind Wind Roche Lobe Overflow Common Envelope Merger AML Kozai W UMa Unstable

23. “Clean Up (Y)our Language!” “Collision” as in “Single Star – Single Star” as in “Resonant Encounter” as in “Collisional Encounter” as in “Collisional Dynamics”

24. “Need to Think Out of the Box”

25. Blue Stragglers Blue stragglers are one part of a larger evolutionary system Yellow Giants Sub-Subgiants

26. “Need to Think Out of the Box” Corollary 1: “Not Strange, Just Different” Blue stragglers and friends are not “anomalous” They are a major stellar evolution channel

27. “Need to Think Out of the Box” Corollary 2: “Its an Interacting Binary!” We need to be prepared to accept that… blue stragglers broadly may not be fundamentally special, and may belong more to the field of interacting binaries than to stellar dynamics. The good news is that is a very rich field to learn from! (e.g, Boffin)

28. “Competitive Advantage” In star clusters … Blue stragglers trace the interface of two classic fields Stellar Dynamics Binary Evolution To move forward in the Ecology of Blue Stragglers, I urge that we keep our focus on star clusters while being deeply cognizant of interacting binaries.

29. “Scientific Method” Especially in observations, we need more overlap and diversity of experimenters

30. Thank You All!

31. Discussion In light of this workshop, what should be the definition of a blue straggler?

32. Thank You to the LOC! Maria Eugenia Gomez Paulina Jiron Dave Jones Andrea Mehner Amy Tyndall