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Winds that Sail on Starlight

Winds that Sail on Starlight. Stan Owocki Bartol Research Institute University of Delaware. Collaborators: Asif Ud-Doula, U. Delaware Vikram Dwarkadas, U. Del. Ken Gayley, U. Iowa David Cohen, Swarthmore Steve Cranmer, CfA Joachim Puls, U. Munich Luc Dessart, Utrecht

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Winds that Sail on Starlight

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  1. Winds that Sail on Starlight Stan Owocki Bartol Research Institute University of Delaware • Collaborators: • Asif Ud-Doula, U. Delaware • Vikram Dwarkadas, U. Del. • Ken Gayley, U. Iowa • David Cohen, Swarthmore • Steve Cranmer, CfA • Joachim Puls, U. Munich • Luc Dessart, Utrecht • Mark Runacres, U. Brussels

  2. Henize 70: LMC SuperBubble WR wind bubble NGC 2359 Superbubble in the Large Magellanic Cloud Wind-Blown Bubbles in ISM Some key scalings: Winds that Sail on Starlight

  3. Pistol Nebula Winds that Sail on Starlight

  4. Eta Carinae Winds that Sail on Starlight

  5. P-Cygni Line Profiles Winds that Sail on Starlight

  6. Modern sails asymmetric form + keel can tack against wind unstable to “keeling over” Line-driving ca. 2000 asymmetric velocity gradient force not || flux spindown & disk inhibition ablation & disk winds radiative braking small-scale instability Sailing vs. Radiative Driving • Early sails • symmetric form • sail mainly with wind • CAK 1975 • 1D spherically symmetric • radially driven outflow Winds that Sail on Starlight

  7. Light’s Momentum • Light transports energy (& information) • But it also has momentum, p=E/c • Usually neglected, because c is so high • But becomes significant for very bright objects, e.g. Lasers, Hot stars, QSO/AGN’s • Key question: how big is force vs. gravity?? Winds that Sail on Starlight

  8. Free Electron Scattering e- Thompson Cross Section th sTh= 2/3 barn= 0.66 x 10-24 cm2 Winds that Sail on Starlight

  9. s L Th g 2 k 4 r c L p m e e el G º = = g 4 GM c p GM grav 2 r G<1 ~ Eddington Parameter • How big is electron scattering force vs. gravity?? • Expressed through a star’s Eddington parameter • For sun, GO ~ 2 x 10-5 • But for hot-stars with L~ 106 LO ; M=10-50 MO Winds that Sail on Starlight

  10. Q~ n t ~ 1015 Hz * 10-8 s ~ 107 Q ~ Z Q ~ 10-4 107 ~ 103 ~ Q s ´ s lines Th g ~ 103 g ´ lines el } 3 if G ´ G >> ~ 10 1 lines el L L = thin Line Scattering: Bound Electron Resonance for high Quality Line Resonance, cross section >> electron scattering Winds that Sail on Starlight

  11. Lsob Optically Thick Line-Absorption in an Accelerating Stellar Wind For strong, optically thick lines: Winds that Sail on Starlight

  12. 0 < a < 1 CAK ensembleof thick & thin lines . * fix M to make line-accel. order gravity * Mass loss rate Velocity law Wind-Momentum Luminosity Law CAK model of steady-state wind inertia gravity CAK line-accel. Equation of motion: Winds that Sail on Starlight

  13. . Wolf-Rayet Winds • “Momentum #” h=Mv¥/(L/c) > 1 • Requires multiple scattering Need line spacing overlap v¥ /Dv= h > 1 Winds that Sail on Starlight

  14. v @ v = g dg~ dv’ r ad @ t i ( k r ° ! t ) ± v ª e @ g r ad 0 ° i! ± v = ± v ¥ U ik ± v @ v 0 w =k = ° U Abbott speed r 0 @ g g v v r ad r ad U = ª ª ª v @ v 0 v 0 v 0 Inward-propagating Abbott waves Winds that Sail on Starlight

  15. Abbott-mode“kinks” Velocity velocity “plateaus” radiative driving modulated by brightness variations Radius shock compression Pulsation-induced wind variability Winds that Sail on Starlight

  16. C IV Model line BW Vul: Observations vs. Model Winds that Sail on Starlight

  17. Rotational Modulation of Hot-Star Winds Radiation hydrodynamics simulation of CIRs in a hot-star wind • Monitoring campaigns of P-Cygni lines formed in hot-star winds also often show modulation at periods comparable to the stellar rotation period. • These may stem from large-scale surface structure that induces spiral wind variation analogous to solar Corotating Interaction Regions. HD64760 Monitored during IUE “Mega” Campaign Winds that Sail on Starlight

  18. u=v/vth Line-Driven Instability Instability with growth rate W ~ g/vth ~ v/Lsob ~100 v/R =>e100 growth! for l < Lsob:dg ~ du Winds that Sail on Starlight

  19. Velocity Density Time snapshot of wind instability simulation CAK Winds that Sail on Starlight

  20. model Dessart & Owocki 2002 WR 140 Lepine & Moffat 1999 WR Star Emission Profile Variability Winds that Sail on Starlight

  21. Radiation Hydro O Star *WR Star WR+O Colliding wind Pure Hydro e.g., V444 Cygni O Star *WR Star “Radiative Braking” Winds that Sail on Starlight

  22. fast dense wind increasing stellar rotation slower wind slower wind Gravity Darkening Winds that Sail on Starlight

  23. W-limit Gravity darkening Langer et al. 1999: Fast spherical wind into slow, dense equatorial flow Dwarkadas et al. 2001 Prolate fast wind into spherical medium Formation of Prolate Nebulae Winds that Sail on Starlight

  24. Vrot (km/s) = 200 250 300 350 400 450 WCD Inhibition by non-radial line-forces Wind Compressed Disk Simulations radial forces only Winds that Sail on Starlight

  25. dvn/dn (1) Stellar oblateness => poleward tilt in radiative flux (2) Pole-equator aymmetry in velocity gradient r N faster polar wind r Max[dvn/dn] Flux slower equatorial wind Vector Line-Force Net poleward line force from: Winds that Sail on Starlight

  26. a. b. -0.9 -90 -0.7 -70 -0.5 -50 -0.3 -30 -0.1 -10 [V (nrf) - V (wcd)] g f f f *sin( )*r/R q 3 2 eq (10 cm/s ) (km/s) Wind rotation spindown from azimuthal line-torque azimuthal line-force ang. mom. loss Winds that Sail on Starlight

  27. Azimuthal Line-Torque DV+<DV_ gf ~DV+-DV_ < 0 Winds that Sail on Starlight

  28. Line-Force in Keplerian Disk Winds that Sail on Starlight

  29. Accretion Disk Windsfrom BAL QSOs Winds that Sail on Starlight

  30. Line-Driven Ablation Net radiative Flux = 0, but glines ~ dvl/dl > 0 ! glines ~ dvl /dl Winds that Sail on Starlight

  31. Be disk formation by RDOME(Radiatively Driven Orbital Mass Ejection) Winds that Sail on Starlight

  32. Density Zoom on density Y- Velocity -1000 vy (km/s) 1000 MHD simulation of line-driven wind Winds that Sail on Starlight

  33. Final state of ZPup isothermal models 93 G ; h* = 0.1 295 G ; h* = 1 165 G ; h* = 0.32 520 G ; h* = 3.2 1650 G ; h* = 32 930 G ; h* = 10 Winds that Sail on Starlight

  34. Summary • Linesefficient way for radiation to drive mass • force depends of l.o.s. velocity gradient • for non-spherical geometry, anisotropic opacity • can get spindown, ablation, WCD inhibition, radiative braking, disk winds • Line-driving very unstable for l < LSob << R* • leads to shocks, clumping, compressible turbulence • may explain X-rays • Current work • effect of NRP, B-field on wind • application to BAL QSO/AGN disk winds • formation of Be disks • Super-Eddington Luminous Blue Variables Winds that Sail on Starlight

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