M. Shara Sept. 26, 2007 Planets, White Dwarfs, Cataclysmic Variables and SNIa in Star Clusters:...

M. Shara Sept. 26, 2007

Planets, White Dwarfs, Planets, White Dwarfs, Cataclysmic Variables and SNIaCataclysmic Variables and SNIain Star Clusters: in Star Clusters: Changing the RulesChanging the Rules

Mike SharaAmerican Museum of Natural History


CollaboratorsCollaborators

J. Hurley

H. Richer

D. Zurek

R. Mardling

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Goal: Completely self-consistent Goal: Completely self-consistent Star Cluster Evolution:Star Cluster Evolution:N-body dynamics + Single + Binary Star Evolution-->N-body dynamics + Single + Binary Star Evolution-->to predict stellar populations/ test against HST datato predict stellar populations/ test against HST data

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OverviewOverview How we do it: hardware and software

The evolution of a cluster and it’s Blue Stragglers (M67)

WDs in clusters…single, divorced, promiscuous

SNIa (double degenerates) in clusters…enhanced rates

CVs in Star Clusters - simulations - the tail wags the dog

Planets in Star Clusters - Making warm Jupiters, eccentric Earths

M. Shara Sept. 26, 2007M. Shara Sept. 26, 2007

Excellent dynamics laboratoriesANDStellar evolution laboratories

Direct integration = O(N3) cost

OPEN & GLOBULAR CLUSTERS

Fokker-Planck and Monte Carlo:

Dynamics/Evolution of 106 – 107 SINGLE starsBUT!Binaries (even 5%) control real clustersN-body essential to study cluster populations,planets


“GRAPE-6”:Hardwired for gravity

simulations: GMm/r2

1018 to 1019 operations/simulation

TeraFlop Computers 1000 Pentiums in a pizza-sized box


NBODY4 software (Aarseth 1999, PASP, 111, 1333)

• includes stellar evolution

• and a binary evolution algorithm

• and as much realism as possible

fitted formulae as opposed to “live” or tables rapid updating of M, R etc. for all stellar types and metallicities done in step with dynamics

tidal evolution, magnetic braking, gravitational radiation, wind accretion, mass-transfer, common-envelope, mergers

perturbed orbits (hardening & break-up), chaotic orbits, exchanges, triple & higher-order subsystems, collisions, etc. … regularization techniques + Hermite integration with GRAPE + block time-step algorithm + external tidal field …


more on the binary evolution method …

Detached Evolution - in timestep tupdate stellar masses

changes to stellar spins

orbital angular momentum and eccentricity changes

evolve stars

check for RLOF

set new timestep

repeat

=> semi-detached evolution


more on the binary evolution method …

Semi-Detached Evolution • Dynamical:

• Steady:

merger or CE (-> merger or binary)

calculate mass-transfer in one orbitdetermine fraction accreted by companionset timestepaccount for stellar windsadjust spins and orbital angular momentumevolve starscheck if donor star still fills Roche-lobecheck for contactrepeat


Initial Conditions

star formation stage is completeall residual gas has been removedall stars are coeval and same composition

distribute masses (IMF) +brown dwarfs? +planets?distribute stellar positions & velocities (density + virial)choose binary fraction and binary masses/separations

lntegrationdynamics (GRAPE ... mostly)stellar & binary evolution (host)formation & dissolution of resonancescollisionsmergers or destructionmass removal, e.g. tidal field

Star Cluster Simulation Procedure

Assumptions


Shortcomings of Current Models

Initial conditions

Neutron star retention

Collision and merger products

Uncertainty of binary evolution parameters

*IMF?*binaries’ mass ratio and separation distributions?

*interface with hydro code

*Real time stellar and binary and merger-product evolution

(Pfahl et al. 2002)*kick velocity at birth?


Simulation of a Rich Open Cluster Initial Conditions

12,000 single stars (0.1 - 50 M) 12,000 binaries (a: flat-log, e: thermal, q: uniform) solar metallicity (Z = 0.02)

Plummer sphere in virial equilibrium circular orbit at Rgc= 8 kpc M ~ 18700 M

tidal radius 32 pcTrh ~ 400 Myr ~ 3 km/snc ~ 200 stars/pc3

6-7 Gyr lifetime4-5 weeks of GRAPE-6 CPU


M67 at 4 Gyr? solar metallicity 50% binaries luminous mass 1000 M in 10pc tidal radius 15pc core radius 0.6pc, half-mass radius 2.5pc


M67 Observed CMD N-body Model CMD

NBS/Nms,2to = 0.15 Rh,BS = 1.6pc half in binaries

NBS/Nms,2to = 0.18 Rh,BS = 1.1pc half in binaries


More than 50% of Blue Stragglers result from dynamical intervention

all observed orbital combinations

perturbations/hardeningexchangestriples

PERIOD

e


20K STAR SIMULATIONS20K STAR SIMULATIONS 16,000 single stars16,000 single stars 2000 stars with Jupiters2000 stars with Jupiters 2000 binaries2000 binaries Kroupa, Tout, Gilmore IMFKroupa, Tout, Gilmore IMF Z=0.004, 0.02Z=0.004, 0.02 q = 0.1 q = 0.1 1.0 1.0 a from log normal distn, peak at 30 aua from log normal distn, peak at 30 au Eccentricity from a thermal distn.Eccentricity from a thermal distn. Planet separations 0.5 Planet separations 0.5 50 au 50 au Galactic tidal field, no shockingGalactic tidal field, no shocking speed ~ 2 km/s, nspeed ~ 2 km/s, nc c ~ 500 stars/pc~ 500 stars/pc33

open cluster: 5 Gyr of evolutionopen cluster: 5 Gyr of evolution


Dynamical Modification of Cluster Populations

aka “Stellar Promiscuity”

500 cases of stellar infidelity730 different stars involved (~15% of cluster)some stars swapped partner once (494)some did it twice (105) three times (48) four (27)five (14) and even 22 times (1) !!Usually the least massive star was ejected


NEVER A DULL MOMENTNEVER A DULL MOMENTOver the entire run (t = 0.0 Over the entire run (t = 0.0

4566.1 Myr):4566.1 Myr):4141 BLUE STRAGGLERS FORMED BLUE STRAGGLERS FORMED 55 CATACLYSMIC VARIABLES CATACLYSMIC VARIABLES 4848 DOUBLE WD SYSTEMS FORMED… DOUBLE WD SYSTEMS FORMED…32/48 ARE NOT PRIMORDIAL 32/48 ARE NOT PRIMORDIAL

BINARIESBINARIES

8 DD collapses 8 DD collapses Likely SN Ia Likely SN Ia


SNIa MotivationSNIa Motivation*SNIa – crucial to cosmology (acceleration)*SNIa – crucial to cosmology (acceleration)

*Corrections to Mv now*Corrections to Mv now handled empirically becausehandled empirically because PROGENITORS ARE UNCERTAINPROGENITORS ARE UNCERTAIN

1) 1) SuperSoftSources (WD +RG)SuperSoftSources (WD +RG) 2) 2) Double Degenerates (WD +WD)Double Degenerates (WD +WD) PREDICTION: SNIa ENHANCED IN STAR PREDICTION: SNIa ENHANCED IN STAR

CLUSTERSCLUSTERS


N-body Evolution Example

Primordial BinaryM1 = 6.88 Msun

M2 = 3.10 Msun

a = 4050 Rsun

After 60 Myr:M1 = 6.26 on AGB

e = 0.0 (tides)RLOF => CEM1 = 1.3 ONeWD

After 434 Myr: M2 = 2.02 on AGB

M1 = 1.3 (symbiotic)RLOF => CE M2 = 0.8 COWD

a = 2500 Rsun

DWD with tgrav ~ 1022 yr

1.3 ONeWD + 0.8 COWD a = 2500 Rsun


1.3 WD0.8 WD DWD

9100 d

2.0 MS

630 Myr

Resonant Exchange(few Myr)

14000 de = 0.63

0.8 WD

perturbed: 6000 d, e = 0.94

CE + CE => DWD (0.35 d) M=1.6

GR -> merger after 10 Gyr Mtot = 1.6 Msun

and then ...

SIRIUS-LIKE BINARY!SIRIUS-LIKE BINARY! 2.0MS

1.3 WD


Are Star Clusters (the) Type Ia Supernova Factories?

8DD =10x expected number of coalescing field double WDs in a modest open cluster Expect >n (globular)/n(open) ~ 103 x enhancement in globulars

dJ/dt mM(m+M) f(e) J a4 GENERAL RELATIVITY

= -K

dP/dt = -k P-5/3

Pcrit ~ 10 hours for ~(1+1) Msun

for gravity waves


DDs which Merge in <10DDs which Merge in <101010 YR with Mtot > 1.4 MsunYR with Mtot > 1.4 Msun

ID #S Types Masses Period/d ID #S Types Masses Period/d 79 80 CO CO 0.826 0.662 8.7096E-03 79 80 CO CO 0.826 0.662 8.7096E-03 33 34 CO CO 0.989 0.664 1.0715E-01 33 34 CO CO 0.989 0.664 1.0715E-01 75 76 CO CO 0.920 0.642 4.3652E-02 75 76 CO CO 0.920 0.642 4.3652E-02 86 8058 CO ONe 0.716 1.241 3.3884E-0186 8058 CO ONe 0.716 1.241 3.3884E-01 63 64 CO CO 0.972 0.665 1.1482E-01 63 64 CO CO 0.972 0.665 1.1482E-01 57 58 ONe CO 1.057 0.574 1.0715E-01 57 58 ONe CO 1.057 0.574 1.0715E-01 61 62 CO CO 1.089 0.536 2.4547E-01 61 62 CO CO 1.089 0.536 2.4547E-01 95 96 CO CO 0.832 0.668 1.1220E-01 95 96 CO CO 0.832 0.668 1.1220E-01

NB! 7 of 8 SYSTEMS ARE PRIMORDIAL; WOULD NOT HAVE NB! 7 of 8 SYSTEMS ARE PRIMORDIAL; WOULD NOT HAVE MERGED IN THE FIELD MERGED IN THE FIELD


Strongly Centrally Strongly Centrally Concentrated “Loaded Guns”Concentrated “Loaded Guns”

MS

DD


SINGLE WD DIVORCED WD

BINARY WD OUTER BINARY WD


M>MChandra

HOW TO FIND “LOADED GUNS”


The White Dwarf Cooling Age and Dynamical History of the Metal-Poor Globular Cluster NGC6397

126 orbits with ACS in Cycle 13 (Mar/Apr 05)

NGC 6397 [Fe/H] = -1.9 core-collapsed

M4 [Fe/H] = -1.3 pre-core-collapse

complements previous observations of M4123 orbits with WFPC2 (Apr 01)

(Hansen et al. 2002, 2004)


11.9 0.4 Gyr

12.1 0.7 Gyr


Contamination of the WD luminosity function (and CMD distribution)

30K, 50% binaries 4 Gyr (Hurley & Shara 2003)


inside Rh

outside Rh


(small) Globular Cluster Model100,000 stars, 5% binaries, Z = 0.001, tidal field20,000 stars at core-collapse (15-16 Gyr)

Rc

Rh


binary frequency < 5%

minimal contamination


Cataclysmic Variable =CV=Classical Nova or Dwarf Nova=

White Dwarf Accreting From a Red Dwarf Companion

Accretion energy viaAccretion disk instability L 100x“dwarf nova” L105-6 Lsun


A White Dwarf Forms INSIDE a Red Giant

Sometimes a companion staris engulfed

1,000,000 X denser thanthe Sun


The long-sought Globular cluster CVs?! (47 Tuc - Grindlay et al)


HST/FUV NGC 2808

Dieball, Knigge, Zurek, Shara, long2005


Non-standard CV formation and evolution

+

0.37 M MS

0.74 M MS

0.71 M MS

0.91 M WD

WD: 0.91 M

MSS: 0.74 M

P=4302d, e=0.97

in cluster coreperturbations -> chaosP=0.52d, circularRLOF

No Common-Envelope!

accelerated CV evolution of individual systems


CV orbital periods

Field

Cluster


Planet MotivationPlanet Motivation

0 hot Jupiters orbiting 34,000 MSS0 hot Jupiters orbiting 34,000 MSSin 47 Tuc….expect ~20 (Gilliland et in 47 Tuc….expect ~20 (Gilliland et

al)al)

Davies & Sigurdsson, Bonnell et al, Davies & Sigurdsson, Bonnell et al, Smith & Bonnell Smith & Bonnell

Most close planets (<0.3 au) survive Most close planets (<0.3 au) survive …WHERE ARE THEY?…WHERE ARE THEY?


N=20,000 STAR N=20,000 STAR SIMULATIONSSIMULATIONS

18,000 single stars18,000 single stars Kroupa, Tout, Gilmore IMFKroupa, Tout, Gilmore IMF Z= 0.017Z= 0.017 100 single stars with Earth +Jupiter OR 100 single stars with Earth +Jupiter OR Neptune + JupiterNeptune + Jupiter Initial a, e of planets = Solar System valuesInitial a, e of planets = Solar System values 2000 binaries with q (mass ratio) = 0.1 2000 binaries with q (mass ratio) = 0.1

1.01.0 a from log normal distn, peak at 30 aua from log normal distn, peak at 30 au Stellar Binaries’ eccentricity: a thermal Stellar Binaries’ eccentricity: a thermal

distn.distn. Galactic tidal field, no shockingGalactic tidal field, no shocking speed ~ 2 km/s, nspeed ~ 2 km/s, nc c ~ 500 stars/pc~ 500 stars/pc33

Massive open cluster: 5 Gyr of evolutionMassive open cluster: 5 Gyr of evolution


N=2,000 STAR SIMULATIONSN=2,000 STAR SIMULATIONS 1400 single stars1400 single stars 600 Binaries600 Binaries 100 single stars with Earth +Jupiter OR 100 single stars with Earth +Jupiter OR Neptune + JupiterNeptune + Jupiter Initial a, e of planets = Solar System Initial a, e of planets = Solar System

valuesvalues speed ~ 2 km/s, nspeed ~ 2 km/s, nc c ~ 10,000 stars/pc~ 10,000 stars/pc33

Sparse open cluster: 5 Gyr of evolutionSparse open cluster: 5 Gyr of evolution


N= 20,000 starsN= 20,000 stars


N=20,000 starsN=20,000 stars


N = 2000 starsN = 2000 stars


N= 20,000 StarsN= 20,000 Stars


4 Encounters “ionize” Jupiter4 Encounters “ionize” Jupiter

AND LEAVE BEHIND AN ECCENTRIC EARTH e =0.6Which escapes the cluster with its host star


Early Wanderlust by NeptuneEarly Wanderlust by Neptune


Ionization of Neptune 4.5 Gyr Ionization of Neptune 4.5 Gyr laterlater


An eccentric Jupiter-Neptune System -An eccentric Jupiter-Neptune System -released into the field at 460 Myr- (from released into the field at 460 Myr- (from

N=2000)N=2000)

“fossil eccentricity”Imprinted by previous cluster environment


JUPITERS

Log a

N

2 40

400 Myr64 Jupiters


SATURNSATURN

JUPITERJUPITER

EARTHEARTH

e a

T Myr


Conclusions – Conclusions – Planets in Star ClustersPlanets in Star Clusters

The Solar System can escape quite intact from The Solar System can escape quite intact from an N=2000 star cluster (Adams+Laughlin 2001)an N=2000 star cluster (Adams+Laughlin 2001)

MANY Tramp planets MUST EXIST!MANY Tramp planets MUST EXIST! More “damage” as N and density increasesMore “damage” as N and density increases Very large eccentricity changes are common Very large eccentricity changes are common

during stellar encountersduring stellar encounters Eccentric singles and doubles are released from Eccentric singles and doubles are released from

clusters into the field (cf Malmberg,Davies et al)clusters into the field (cf Malmberg,Davies et al) ““Tepid” Jupiters are easy to form…a = 3 - 7 AUTepid” Jupiters are easy to form…a = 3 - 7 AU No “hot” Jupiters seen yetNo “hot” Jupiters seen yet Coming: Jupiter + Saturn; 3-4 planetsComing: Jupiter + Saturn; 3-4 planets


CONCLUSIONS – SNIa and DD

*Beware of DD in age-dating the *Beware of DD in age-dating the UniverseUniverse

**HARDENING OF DDs MANUFACTURESHARDENING OF DDs MANUFACTURES

“ “LOADED GUNS” IN CLUSTERS….LOADED GUNS” IN CLUSTERS….

Grav. Radiation does the restGrav. Radiation does the rest

**Long hardening timescaleLong hardening timescaleNo z peak No z peak in SNIa (J. Tonry)in SNIa (J. Tonry)

**Look in clusters (eg M67, NGC 188) Look in clusters (eg M67, NGC 188) forfor

very short period DDs (~5 today)very short period DDs (~5 today)


SINGLE JUPITERS (0.05-50 AU) IN AN OPEN SINGLE JUPITERS (0.05-50 AU) IN AN OPEN CLUSTERCLUSTER

LIBERATED FROM PARENT

ESCAPING FROM CLUSTER


EARTHS

Log a

N

400 Myr22 Earths


eccentricity

NEarths

400 Myr22 Earths


PLANET LIBERATION LOCATIONSPLANET LIBERATION LOCATIONS


PLANET LIBERATION PLANET LIBERATION VELOCITIESVELOCITIES

M. Shara Sept. 26, 2007 Planets, White Dwarfs, Cataclysmic Variables and SNIa in Star Clusters:...

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