Solar-Mass Binary Stars in Open Clusters

Ecology of Blue Stragglers:Closing Thoughtsand Discussion

1Two Perspectives are Better than OneMicroEconomicsMicroAstronomicsMacroEconomicsMacroAstronomicsBimodal radial distributionsDual CMD sequencesKudos to Ferraro et al. for making data available!

LanzoniDalessandro

2MicroAstronomicsMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence of FBSS on fbin, photo KniggeSantana

3MicroAstronomicsMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingPeretsChen

Kudos to Davies!

McMillanKudos to Ahumada for catalogs4MicroAstronomicsBinary frequenciesBinary period distributionsBinary secondary starsMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingGeller5All of the preceding:High binary fractionDeficit of short (and very long) periodsLow orbital eccentricitiesSmall mass functionsNo visible secondaries

tell us that FBS are a species sui generis

Hard binary frequency 76% Typical orbital period 1000 days Typical secondary mass 0.5 Mo Lower orbital eccentricities All SB1Preston(Field)Mathieu(NGC 188)MicroAstronomicsBinary frequenciesBinary period distributionsBinary secondary starsModestly rapidly rotatingMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingLovisi

7MicroAstronomicsBinary frequenciesBinary period distributionsBinary secondary starsModestly rapidly rotatingEarly chemical abundancesEarly mass measurementsMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingMucciarelli

1.58 Mo2.52 Mo1.07 dS1082

8MicroAstronomicsBinary frequenciesBinary period distributionsBinary secondary starsModestly rapidly rotatingEarly chemical abundancesEarly mass measurementsEvolutionary tracksMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingMass transfer modeling

Sills

Ivanova9MicroAstronomicsBinary frequenciesBinary period distributionsBinary secondary starsModestly rapidly rotatingEarly chemical abundancesEarly mass measurementsEvolutionary tracksMacroAstronomicsBimodal radial distributionsDual CMD sequencesNo dependence on collision rateDependence on environment (N vs r)Dependence on Mcore, fbinPopulation synthesisCluster dynamical modelingMass transfer modelingTwo Perspectives are Better than One10Outstanding QuestionsIn 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! )11What is the CMD telling us? Do we understand CMD locations of BS? Should we believe anything from (standard) evolution theory?Alison I dont understand how toget such low luminosities.Natasha I dont understand how to get those masses.xPhotometricDynamical1.5 Mo

Outstanding Questions

12What 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?

Outstanding Questions

13Outstanding QuestionsDo stellar collisions occur?What is the CMD telling us?

Leigh, Knigge, Sills, Perets, Sarajedini & Glebbeek (2012)

14Outstanding QuestionsDo stellar collisions occur?What are the products? Where are the products?What is the CMD telling us?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 201115Outstanding QuestionsDo stellar collisions occur?What is the CMD telling us?What can we learn from angular momentum?What are we missing by not considering magnetic fields?7 Gyr2.5 Gyr

16Outstanding QuestionsDo stellar collisions occur?What is the CMD telling us?What can we learn from chemical abundances? Is there hope of microastronomic diagnostics of formation?What can we learn from angular momentum?What are we missing by not considering magnetic fields?

Need to learn more from George P. about s-process abundances!17Outstanding QuestionsDo stellar collisions occur?What is the CMD telling us?What can we learned from evolved populations?Possible indirect handle on massesWhat can we learn from chemical abundances?What can we learn from angular momentum?What are we missing by not considering magnetic fields?18Outstanding QuestionsDo stellar collisions occur?What is the CMD telling us?What can we learned from evolved populations?Possible indirect handle on massesWhat can we learn from chemical abundances?What can we learn from angular momentum?What are we missing by not considering magnetic fields?Are there circumstellar diagnostics for any of these processes? Has anyone looked?19How Shall We Move Forward?

WisconsinBadger

20Clean Up (Y)our Language!Binary

as in Binary Frequencyas in Close BinaryMathieuDaviesChen

binaryas in Consistent with binary formation channel21Clean Up (Y)our Language!Mass TransferAs in Consistent with mass transfer originRoche Lobe OverflowCase ACase BCase CWindWind Roche Lobe OverflowCommon EnvelopeMergerAMLKozaiW UMaUnstable

22Clean Up (Y)our Language!Collisionas in Single Star Single Staras in Resonant Encounteras in Collisional Encounteras in Collisional Dynamics23Need to Think Out of the Box

24

Blue StragglersSub-SubgiantsYellow Giants

Blue stragglers are one part of a larger evolutionary system25Corollary 1: Not Strange, Just Different

Need to Think Out of the BoxBlue stragglers and friends are not anomalousThey are a major stellar evolution channel

26We need to be prepared to accept thatblue stragglers broadly may not be fundamentally special,Corollary 2: Its an Interacting Binary!Need to Think Out of the Boxand may belong more to the field of interacting binariesthan to stellar dynamics.The good news is that is a very rich fieldto learn from!(e.g, Boffin)27

Competitive AdvantageIn star clusters

Blue stragglers trace the interface of two classic fields

Stellar Dynamics

Binary EvolutionTo move forward in the Ecology of Blue Stragglers,I urge that we keep our focus on star clusterswhile being deeply cognizant of interacting binaries.28Scientific Method

Especially in observations,

we need more overlap and diversity of experimenters

29Thank You All!

30DiscussionIn light of this workshop,

what should be the definition of a blue straggler?

31Thank You to the LOC!

Maria Eugenia GomezPaulina JironDave JonesAndrea MehnerAmy Tyndall

32

-./001.2)**03

( %*6!6

4!.

%718

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6M2 ( MO )

0

20

40

60

80

100fre

quen

cy (%

)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6M2 ( MO )

0

20

40

60

80

100fre

quen

cy (%

)

-./001.2)**03

( %*6!6

4!.

%718

Results : C & O