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Exploring Stellar Winds that Sails on Starlight: A Look Into Astrophysical Phenomena

Delve into the intriguing realm of stellar winds sailing on starlight, investigating various phenomena like wind bubbles, line driving effects, and radiation hydrodynamics in hot star winds. Discover key scalings and interactions between light, momentum, and gravitational forces shaping these celestial occurrences. Unravel the complexities of line-driven instabilities, stellar wind variability, and the formation of unique nebula structures affected by stellar rotation and radiative forces. Join us on a cosmic journey through the mysteries of the universe.

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Exploring Stellar Winds that Sails on Starlight: A Look Into Astrophysical Phenomena

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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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