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 Wind-Blown Bubbles in ISM Some key scalings: WR wind bubble NGC 2359 Superbubble in the Large Magellanic Cloud STScI 11/07/01 Wind that Sail on Starlight 2

3 Pistol Nebula STScI 11/07/01 Wind that Sail on Starlight 3

4 Eta Carinae STScI 11/07/01 Wind that Sail on Starlight 4

5 P-Cygni Line Profiles STScI 11/07/01 Wind that Sail on Starlight 5

6 Sailing vs. Radiative Driving Early sails symmetric form sail mainly with wind Modern sails asymmetric form + keel can tack against wind unstable to keeling over CAK D spherically symmetric radially driven outflow Line-driving ca asymmetric velocity gradient force not flux spindown & disk inhibition ablation & disk winds radiative braking small-scale instability STScI 11/07/01 Wind that Sail on Starlight 6

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?? STScI 11/07/01 Wind that Sail on Starlight 7

8 Free Electron Scattering e - Thompson Cross Section th σ Th = 2/3 barn= 0.66 x cm 2 STScI 11/07/01 Wind that Sail on Starlight 8

9 Eddington Parameter How big is electron scattering force vs. gravity?? Expressed through a star s Eddington parameter Γ g L σth el 4πr 2 c µ = e = g grav GM 2 r Γ<1 ~ κ e L 4πGMc For sun, Γ O ~ 2 x 10-5 But for hot-stars with L~ 10 6 L O ; M=10-50 M O STScI 11/07/01 Wind that Sail on Starlight 9

10 Line Scattering: Bound Electron Resonance for high Quality Line Resonance, cross section >> electron scattering Q~ ν τ ~ Hz * 10-8 s ~ 10 7 Q ~ Z Q ~ ~ 10 3 σ lines ~Q σ Th g lines ~10 3 g el Γ lines ~10 3 Γ el >> 1 } if L = L thin STScI 11/07/01 Wind that Sail on Starlight 10

11 Optically Thick Line-Absorption in an Accelerating Stellar Wind For strong, optically thick lines: L sob vth τ κρ dv / dr g thick gthin ~ ~ τ 1 dv ρ dr STScI 11/07/01 Wind that Sail on Starlight 11

12 Equation of motion: CAK model of steady-state wind inertia gravity CAK line-accel. GM vv + r fql r r vv MQ. * fix M to make line-accel. order gravity * α 0 < α < 1 CAK ensemble of thick & thin lines Ṁ Mass loss rate L c 2 Q Γ 1 Γ 1 1 α Velocity law v() r v ( 1 R / r) ~v esc Wind-Momentum Luminosity Law Ṁ v L 1 α α 06. STScI 11/07/01 Wind that Sail on Starlight 12

13 Wolf-Rayet Winds Momentum # η=mv /(L/c) > 1 Requires multiple scattering. Need line spacing overlap v / v= η > 1 STScI 11/07/01 Wind that Sail on Starlight 15

14 Inward-propagating Abbott waves v t = g r ad δv e i(kr ωt) w/k = U iω δv = grad δv v U ikδv Abbott speed v δg~ δv U = g rad v g rad v vv v v r STScI 11/07/01 Wind that Sail on Starlight 17

15 Pulsation-induced wind variability Velocity Abbott-mode kinks radiative driving modulated by brightness variations shock compression velocity plateaus Radius STScI 11/07/01 Wind that Sail on Starlight 18

16 BW Vul: Observations vs. Model C IV Model line STScI 11/07/01 Wind that Sail on Starlight 20

at periods comparable to the stellar rotation period.

17 Rotational Modulation of Hot-Star Winds HD64760 Monitored during IUE Mega Campaign 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. STScI 11/07/01 Wind that Sail on Starlight 21

18 Line-Driven Instability u=v/v th for λ < L sob : δg ~ δu Instability with growth rate Ω ~ g/v th ~ v/l sob ~100 v/r => e 100 growth! STScI 11/07/01 Wind that Sail on Starlight 23

19 Time snapshot of wind instability simulation 1500 CAK Velocity (km/s) Velocity Density log( ρ) g/cm Height (R * ) -15 STScI 11/07/01 Wind that Sail on Starlight 26

20 WR Star Emission Profile Variability WR 140 Lepine & Moffat 1999 model Dessart & Owocki 2002 STScI 11/07/01 Wind that Sail on Starlight 30

21 WR+O Colliding wind Pure Hydro e.g., V444 Cygni O Star *WR Star Radiation Hydro Radiative Braking O Star *WR Star STScI 11/07/01 Wind that Sail on Starlight 32

22 Gravity Darkening increasing stellar rotation fast dense wind slower wind slower wind STScI 11/07/01 Wind that Sail on Starlight 36

23 Formation of Prolate Nebulae Ω-limit Langer et al. 1999: Fast spherical wind into slow, dense equatorial flow Gravity darkening Dwarkadas et al Prolate fast wind into spherical medium STScI 11/07/01 Wind that Sail on Starlight 37

radial forces only Wind Compressed Disk Simulations Vrot (km/s) = 200 250 300 350 400

24 radial forces only Wind Compressed Disk Simulations Vrot (km/s) = WCD Inhibition by non-radial line-forces STScI 11/07/01 Wind that Sail on Starlight 40

25 Net poleward line force from: Vector Line-Force r r r r r g ~ line dω n I n [ ( n )] * v α Ω * dv n /dn (1) Stellar oblateness => poleward tilt in radiative flux N Flux r (2) Pole-equator aymmetry in velocity gradient faster polar wind Max[dv n /dn] r slower equatorial wind STScI 11/07/01 Wind that Sail on Starlight 41

26 Wind rotation spindown from azimuthal line-torque azimuthal a. line-force b. ang. mom. loss g φ [V φ (nrf) - V φ (wcd)] -10 (10 3 cm/s 2 ) *sin( θ )*r/r eq (km/s) STScI 11/07/01 Wind that Sail on Starlight 42

27 Azimuthal Line-Torque I + I - I + I - I - I + V + < V_ g φ ~ V + - V_ < 0 STScI 11/07/01 Wind that Sail on Starlight 43

28 Line-Force in Keplerian Disk dvz/dz dvr/dr z r STScI 11/07/01 Wind that Sail on Starlight 44

29 Accretion Disk Winds from BAL QSOs Xray source UV black hole radiating accretion disk failed wind X-ray shield UV line-driven Accretion Disk Wind STScI 11/07/01 Wind that Sail on Starlight 45

30 Line-Driven Ablation Net radiative Flux = 0, but g lines ~ dv l /dl > 0! g lines ~ dv l /dl STScI 11/07/01 Wind that Sail on Starlight 46

31 Be disk formation by RDOME (Radiatively Driven Orbital Mass Ejection) STScI 11/07/01 Wind that Sail on Starlight 47

32 MHD simulation of line-driven wind Y- Velocity Density Zoom on density v y (km/s) 1000 STScI 11/07/01 Wind that Sail on Starlight 49

Final state of ZPup isothermal models 93 G ; η * = 0.1 165 G ; η * = 0.

33 Final state of ZPup isothermal models 93 G ; η * = G ; η * = G ; η * = G ; η * = G ; η * = G ; η * = 32 STScI 11/07/01 Wind that Sail on Starlight 51

34 Summary Lines efficient 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 λ < L Sob << 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 STScI 11/07/01 Wind that Sail on Starlight 52

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