Population synthesis with Population synthesis with dynamicsdynamics

Natasha Ivanova

MODEST-6August 2005

or or the problems that we facethe problems that we face

What is population synthesis?What is population synthesis?

EvolutionaryEvolutionary Population Synthesis is the method of Population Synthesis is the method of direct modeling of large populations of non-direct modeling of large populations of non-interacting objects (single or binaries in our case) interacting objects (single or binaries in our case) with non-trivial (non-describable by simple analytic) with non-trivial (non-describable by simple analytic) evolution.evolution.

The evolution for an object is followed from its birth till The evolution for an object is followed from its birth till the desired moment. the desired moment.

The goals:The goals:a)a) to see how the population looks like from to see how the population looks like from

statistical point of viewstatistical point of viewb)b) to check if theory works OK and produces the to check if theory works OK and produces the

same number of rare objects as observedsame number of rare objects as observedc)c) predict new objects!predict new objects!

Collision time Collision time collcoll: : time between two time between two

successive collisions, successive collisions, collcoll = 1/n= 1/nccSS

Hardness Hardness : : ratio between binary binding ratio between binary binding energy and kinetic energy of an average objectenergy and kinetic energy of an average object

Soft binaries Soft binaries <1<1: : get softer get softer (Heggie 1975);(Heggie 1975); very likely to be destroyed through ionizationvery likely to be destroyed through ionization

Hard binaries Hard binaries >1>1: : get harder; the get harder; the encounter can result in the exchange of the encounter can result in the exchange of the companion (smaller mass component is replaced companion (smaller mass component is replaced by more massive intruder); very hard binary is by more massive intruder); very hard binary is likely to merge likely to merge (Fregeau et al. 2004)(Fregeau et al. 2004)

Basics of the binary Basics of the binary dynamicsdynamics

Why do we care about binaries?Why do we care about binaries? Interacted and destroyed binaries Interacted and destroyed binaries

Interacted and survived binariesInteracted and survived binaries

Non-Interacted binariesNon-Interacted binaries

Among stars with the initial masses > 0.6 Msun

only 8%only 8% are both hard and did not have interactions…

Magnetic brakingMagnetic braking Mass transfer eventsMass transfer events Mergers Mergers Common envelope eventsCommon envelope events Tidal circularization and synchronization Tidal circularization and synchronization Accretion on WDs, Ia SN and subCh Ia Accretion on WDs, Ia SN and subCh Ia SN kicks and NS-retention: e-c SN?SN kicks and NS-retention: e-c SN?

Triples?!Triples?!

What do we NEED to take into What do we NEED to take into account for binaries and why life account for binaries and why life is uncertainis uncertain

IMFIMF Mass ratio distribution?Mass ratio distribution?

How to pick the secondary?How to pick the secondary? Does q depend on the primary masses?Does q depend on the primary masses? Does q depend on binary periods?Does q depend on binary periods? What is about “twins”?What is about “twins”?

Periods distribution?Periods distribution? Eccentricities distribution? Eccentricities distribution? Initial binaries/triples/quadruples/quintuples and Initial binaries/triples/quadruples/quintuples and

sextuples fractions?sextuples fractions?

A few spices before you start to A few spices before you start to boil the soupboil the soup

Moscow (Yungleson, Tutukov, Lipunov, Moscow (Yungleson, Tutukov, Lipunov, Postnov,…) Postnov,…)

Seba (Portegiez Zwart, Tout, Verbunt,…)Seba (Portegiez Zwart, Tout, Verbunt,…) SSE & BSE (Hurley, Pols, Tout) SSE & BSE (Hurley, Pols, Tout)

Kalogera, BelczynskiKalogera, Belczynski Willems, KolbWillems, Kolb ……

Brussel code (Vanbeveren & CBrussel code (Vanbeveren & Coo): interpolation ): interpolation between tracks for massive starsbetween tracks for massive stars

Podsiadlowski, Rappaport, Pfahl & Han : Podsiadlowski, Rappaport, Pfahl & Han : detailed binary tracks for specific classes of detailed binary tracks for specific classes of systems (Ia SN, LMXBs, sdB …)systems (Ia SN, LMXBs, sdB …)

Some currently existing Some currently existing Population Synthesis codes for Population Synthesis codes for interacting binariesinteracting binaries

o fast and robusto correct and powerful (not restricted to a certain

class of objects)

Time-scale: < one month on a modest 32-CPUs cluster (at 50%Memory-resources: 4Gb of memory (NO swapping!)

250,000 Msun GC: ~ 1,000,000 stars: < 40 seconds per star one star should not take more than 40kb in memory.

An unavoidable fact: the evolution of a single star takes much less than the evolution of a binary, if one speaks about an interacting binary.

So the code is better be able to evolve a single star on a time-scale of few seconds.

Any wishes?Any wishes?

SS encounters SS encounters Mergers in physical collisionsMergers in physical collisions Binary formations via physical collisions Binary formations via physical collisions Binary formations via tidal capturesBinary formations via tidal captures

Three and four body encountersThree and four body encounters MT is interruptedMT is interrupted Eccentricity is changedEccentricity is changed Exchange occurred and companions are now Exchange occurred and companions are now

misaligned and not any more on the corotationmisaligned and not any more on the corotation (multiple) physical collisions, including “dynamical” CE(multiple) physical collisions, including “dynamical” CE triples formationtriples formation

GC: evolution is perturbed!GC: evolution is perturbed!

How to deal with all the mess?How to deal with all the mess?

Learn binary evolution in the fieldLearn binary evolution in the field Build a “scenario processor” for all eventsBuild a “scenario processor” for all events Analyze what happens - does it make any Analyze what happens - does it make any

sense?sense? Treat specific circumstances with great Treat specific circumstances with great

detailsdetails Re-runRe-run Run to observersRun to observers Get from observers their results and sit for Get from observers their results and sit for

a while thinking why there is no common a while thinking why there is no common languagelanguage

Formation of CV binaries: CE or Formation of CV binaries: CE or encounter?encounter?

Field, non-eccentric binariesField, non-eccentric binaries

CVs formation: main formation CVs formation: main formation channelschannels

MS-MS

CV

single binary

BS/BB

BS/BBSS

Destr

CollisExch

CE

Merger

Coll RG

Exch

CE10%

40%

15% 35%

CVs: population of WDsCVs: population of WDs

Field “Typical” clusterField “Typical” cluster

Simulaions vs observationsSimulaions vs observations

Simulations ObservationsSimulations Observations

PS and dynamics: some currently PS and dynamics: some currently active codesactive codes

Hurley - open clusters, M67.Hurley - open clusters, M67. SeBa - IMBH formation, open clusters ecologySeBa - IMBH formation, open clusters ecology Brussel - young clusters with massive starsBrussel - young clusters with massive stars Freitag - IMBH formation, Galactic centerFreitag - IMBH formation, Galactic center Fregeau, Gurkan, Rasio - IMBH formation, mass Fregeau, Gurkan, Rasio - IMBH formation, mass

segregation in globular clusters with full IMFsegregation in globular clusters with full IMF Ivanova, Belczynski, Fregeau, Rasio - binary Ivanova, Belczynski, Fregeau, Rasio - binary

fractions, compact binaries formation and fractions, compact binaries formation and evolution in globular clustersevolution in globular clusters

Postnov - NS retention, MSPsPostnov - NS retention, MSPs

Future of PS codes with dynamicsFuture of PS codes with dynamics

Bill Paxton’s “EZ” code (Eggleton-refasted): Bill Paxton’s “EZ” code (Eggleton-refasted): one minute per single star one minute per single star Saul Rappaport and his students at MIT: large Saul Rappaport and his students at MIT: large

population study of binary evolution and RLO.population study of binary evolution and RLO. 30,000 binaries in 24 hours at 35 nodes 30,000 binaries in 24 hours at 35 nodes (~2 minutes/RLO binary!!!)(~2 minutes/RLO binary!!!) http://theory.kitp.ucsb.edu/~paxtonhttp://theory.kitp.ucsb.edu/~paxton