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Planets, White Dwarfs, Cataclysmic Variables and SNIa in Star Clusters: Changing the Rules

Planets, White Dwarfs, Cataclysmic Variables and SNIa in Star Clusters: Changing the Rules. Mike Shara American Museum of Natural History. Collaborators. J. Hurley H. Richer D. Zurek R. Mardling.

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Planets, White Dwarfs, Cataclysmic Variables and SNIa in Star Clusters: Changing the Rules

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  1. Planets, White Dwarfs, Cataclysmic Variables and SNIain Star Clusters: Changing the Rules Mike Shara American Museum of Natural History M. Shara Sept. 26, 2007

  2. Collaborators J. Hurley H. Richer D. Zurek R. Mardling M. Shara Sept. 26, 2007

  3. Goal: Completely self-consistent Star Cluster Evolution:N-body dynamics + Single + Binary Star Evolution-->to predict stellar populations/ test against HST data M. Shara Sept. 26, 2007

  4. Overview • 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, 2007

  5. OPEN & GLOBULAR CLUSTERS • Excellent dynamics laboratories • AND • Stellar evolution laboratories • Direct integration = O(N3) cost Fokker-Planck and Monte Carlo: Dynamics/Evolution of 106 – 107SINGLE stars BUT! Binaries (even 5%) control real clusters N-body essential to study cluster populations, planets M. Shara Sept. 26, 2007

  6. TeraFlop Computers 1000 Pentiums in a pizza-sized box “GRAPE-6”: Hardwired for gravity simulations: GMm/r2 • 1018 to 1019 operations/simulation M. Shara Sept. 26, 2007

  7. 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 … M. Shara Sept. 26, 2007

  8. more on the binary evolution method … Detached Evolution - in timestep t • update stellar masses • changes to stellar spins • orbital angular momentum and eccentricity changes • evolve stars • check for RLOF • set new timestep • repeat => semi-detached evolution M. Shara Sept. 26, 2007

  9. more on the binary evolution method … Semi-Detached Evolution • Dynamical: • Steady: • merger or CE (-> merger or binary) • calculate mass-transfer in one orbit • determine fraction accreted by companion • set timestep • account for stellar winds • adjust spins and orbital angular momentum • evolve stars • check if donor star still fills Roche-lobe • check for contact • repeat M. Shara Sept. 26, 2007

  10. Star Cluster Simulation Procedure Assumptions • star formation stage is complete • all residual gas has been removed • all 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 Initial Conditions • ntegration dynamics (GRAPE ... mostly) stellar & binary evolution (host) formation & dissolution of resonances collisionsmergers or destruction mass removal, e.g. tidal field M. Shara Sept. 26, 2007

  11. 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? (Pfahl et al. 2002) *kick velocity at birth? *interface with hydro code *Real time stellar and binary and merger-product evolution M. Shara Sept. 26, 2007

  12. 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 pc • Trh ~ 400 Myr •  ~ 3 km/s • nc ~ 200 stars/pc3 • 6-7 Gyr lifetime • 4-5 weeks of GRAPE-6 CPU M. Shara Sept. 26, 2007

  13. solar metallicity  • 50% binaries  • luminous mass 1000 M in 10pc  • tidal radius 15pc  • core radius 0.6pc, half-mass radius 2.5pc  M67 at 4 Gyr? M. Shara Sept. 26, 2007

  14. 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 M. Shara Sept. 26, 2007

  15. More than 50% of Blue Stragglers result from dynamical intervention all observed orbital combinations e • perturbations/hardening • exchanges • triples PERIOD M. Shara Sept. 26, 2007

  16. 20K STAR SIMULATIONS • 16,000 single stars • 2000 stars with Jupiters • 2000 binaries • Kroupa, Tout, Gilmore IMF • Z=0.004, 0.02 • q = 0.1  1.0 • a from log normal distn, peak at 30 au • Eccentricity from a thermal distn. • Planet separations 0.5  50 au • Galactic tidal field, no shocking • speed ~ 2 km/s, nc ~ 500 stars/pc3 • open cluster: 5 Gyr of evolution M. Shara Sept. 26, 2007

  17. Dynamical Modification of Cluster Populations aka “Stellar Promiscuity” 500 cases of stellar infidelity 730 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 M. Shara Sept. 26, 2007

  18. NEVER A DULL MOMENT Over the entire run (t = 0.0  4566.1 Myr): 41 BLUE STRAGGLERS FORMED 5 CATACLYSMIC VARIABLES 48 DOUBLE WD SYSTEMS FORMED… 32/48 ARE NOT PRIMORDIAL BINARIES 8 DD collapses  Likely SN Ia M. Shara Sept. 26, 2007

  19. SNIa Motivation *SNIa – crucial to cosmology (acceleration) *Corrections to Mv now handled empirically because PROGENITORS ARE UNCERTAIN 1) SuperSoftSources (WD +RG) 2) Double Degenerates (WD +WD) PREDICTION: SNIa ENHANCED IN STAR CLUSTERS M. Shara Sept. 26, 2007

  20. N-body Evolution Example Primordial Binary M1 = 6.88 Msun M2 = 3.10 Msun a = 4050 Rsun After 60 Myr: M1 = 6.26 on AGB e = 0.0 (tides) RLOF => CE M1 = 1.3 ONeWD After 434 Myr: M2 = 2.02 on AGB M1 = 1.3 (symbiotic) RLOF => CE M2 = 0.8 COWD 1.3 ONeWD + 0.8 COWD a = 2500 Rsun a = 2500 Rsun M. Shara Sept. 26, 2007 DWD with tgrav ~ 1022 yr

  21. and then ... 1.3 WD SIRIUS-LIKE BINARY! 2.0MS 0.8 WD DWD 9100 d 1.3 WD 14000 d e = 0.63 Resonant Exchange (few Myr) • perturbed: 6000 d, e = 0.94 • CE + CE => DWD (0.35 d) M=1.6 • GR -> merger after 10 Gyr • Mtot = 1.6 Msun 630 Myr 2.0 MS 0.8 WD M. Shara Sept. 26, 2007

  22. dJ/dtmM(m+M) f(e) = -K J a4GENERAL RELATIVITY dP/dt = -k P-5/3 Pcrit ~ 10 hours for ~(1+1) Msun for gravity waves 8DD =10x expected number of coalescing field double WDs in a modest open cluster Expect >n(globular)/n(open) ~ 103 x enhancement in globulars Are Star Clusters (the) Type Ia Supernova Factories? M. Shara Sept. 26, 2007

  23. DDs which Merge in <1010 YR with Mtot > 1.4 Msun ID #S Types Masses Period/d 79 80 CO CO 0.826 0.662 8.7096E-03 33 34 CO CO 0.989 0.664 1.0715E-01 75 76 CO CO 0.920 0.642 4.3652E-02 86 8058 CO ONe 0.716 1.241 3.3884E-01 63 64 CO CO 0.972 0.665 1.1482E-01 57 58 ONe CO 1.057 0.574 1.0715E-01 61 62 CO CO 1.089 0.536 2.4547E-01 95 96 CO CO 0.832 0.668 1.1220E-01 NB! 7 of 8 SYSTEMS ARE PRIMORDIAL; WOULD NOT HAVE MERGED IN THE FIELD M. Shara Sept. 26, 2007

  24. Strongly Centrally Concentrated “Loaded Guns” DD MS M. Shara Sept. 26, 2007

  25. DIVORCED WD SINGLE WD OUTER BINARY WD BINARY WD M. Shara Sept. 26, 2007

  26. M>MChandra HOW TO FIND “LOADED GUNS” M. Shara Sept. 26, 2007

  27. 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) complements previous observations of M4 • 123 orbits with WFPC2 (Apr 01) NGC 6397  [Fe/H] = -1.9  core-collapsed M4  [Fe/H] = -1.3  pre-core-collapse (Hansen et al. 2002, 2004) M. Shara Sept. 26, 2007

  28. 11.9  0.4 Gyr 12.1  0.7 Gyr M. Shara Sept. 26, 2007

  29. Contamination of the WD luminosity function (and CMD distribution) 30K, 50% binaries  4 Gyr (Hurley & Shara 2003) M. Shara Sept. 26, 2007

  30. M. Shara Sept. 26, 2007

  31. M. Shara Sept. 26, 2007

  32. inside Rh outside Rh M. Shara Sept. 26, 2007

  33. (small) Globular Cluster Model • 100,000 stars, 5% binaries, Z = 0.001, tidal field • 20,000 stars at core-collapse (15-16 Gyr) Rh Rc M. Shara Sept. 26, 2007

  34. M. Shara Sept. 26, 2007

  35. M. Shara Sept. 26, 2007

  36. binary frequency < 5% minimal contamination M. Shara Sept. 26, 2007

  37. Cataclysmic Variable =CV=Classical Nova or Dwarf Nova=White Dwarf Accreting From a Red Dwarf Companion Accretion energy via Accretion disk instability L 100x “dwarf nova” L105-6 Lsun M. Shara Sept. 26, 2007

  38. A White Dwarf Forms INSIDE a Red Giant Sometimes a companion star is engulfed 1,000,000 X denser than the Sun M. Shara Sept. 26, 2007

  39. The long-sought Globular cluster CVs?! (47 Tuc - Grindlay et al) M. Shara Sept. 26, 2007

  40. HST/FUV NGC 2808 Dieball, Knigge, Zurek, Shara, long 2005 M. Shara Sept. 26, 2007

  41. Non-standard CV formation and evolution 0.74 M MS MSS: 0.74 M + 0.91 M WD P=4302d, e=0.97 WD: 0.91 M 0.71 M MS • in cluster core • perturbations -> chaos • P=0.52d, circular • RLOF 0.37 M MS No Common-Envelope! accelerated CV evolution of individual systems M. Shara Sept. 26, 2007

  42. CV orbital periods Field Cluster M. Shara Sept. 26, 2007

  43. Planet Motivation 0 hot Jupiters orbiting 34,000 MSS in 47 Tuc….expect ~20 (Gilliland et al) Davies & Sigurdsson, Bonnell et al, Smith & Bonnell  Most close planets (<0.3 au) survive …WHERE ARE THEY? M. Shara Sept. 26, 2007

  44. N=20,000 STAR SIMULATIONS • 18,000 single stars • Kroupa, Tout, Gilmore IMF • Z= 0.017 • 100 single stars with Earth +Jupiter OR • Neptune + Jupiter • Initial a, e of planets = Solar System values • 2000 binaries with q (mass ratio) = 0.1  1.0 • a from log normal distn, peak at 30 au • Stellar Binaries’ eccentricity: a thermal distn. • Galactic tidal field, no shocking • speed ~ 2 km/s, nc ~ 500 stars/pc3 • Massive open cluster: 5 Gyr of evolution M. Shara Sept. 26, 2007

  45. N=2,000 STAR SIMULATIONS • 1400 single stars • 600 Binaries • 100 single stars with Earth +Jupiter OR • Neptune + Jupiter • Initial a, e of planets = Solar System values • speed ~ 2 km/s, nc ~ 10,000 stars/pc3 • Sparse open cluster: 5 Gyr of evolution M. Shara Sept. 26, 2007

  46. N= 20,000 stars M. Shara Sept. 26, 2007

  47. N=20,000 stars M. Shara Sept. 26, 2007

  48. N = 2000 stars M. Shara Sept. 26, 2007

  49. N= 20,000 Stars M. Shara Sept. 26, 2007

  50. 4 Encounters “ionize” Jupiter AND LEAVE BEHIND AN ECCENTRIC EARTH e =0.6 Which escapes the cluster with its host star M. Shara Sept. 26, 2007

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