Links Between Pulsations & Line-Driven Mass Loss in Massive Stars Stan Owocki Bartol Research Institute University of Delaware IAU Colloquium #185 Leuven, Belgium July 26-31, 2001 Possible

July 30, 2001IAUC 1852 Outline Key properties of line-driven mass loss Wind variability –Discrete Absorption Components –Periodic Absorption Modulations Candidates for Pulsation Wind Connection –BW Vul –EZ CMa = WR 6 Possible role of pulsation in initiating mass loss –WR winds –B e disks

July 30, 2001IAUC 1853 Optically Thick Line-Absorption in an Accelerating Stellar Wind L sob For strong, optically thick lines:

July 30, 2001IAUC 1854  < 1 CAK ensemble of thick & thin lines CAK model of steady-state wind inertiagravityCAK line-force Solve for: Mass loss rate Wind-Momentum Luminosity Law Velocity law Equation of motion:

July 30, 2001IAUC 1855 Inward-propagating Abbott waves ±vªe i(kr°!t) 0 rad ±v 0 ¥Uik±v w=k=°U 0 ª g r v 0 ª vv 0 v =g r v r  g~  v’ Abbott speed

July 30, 2001IAUC 1856 Inward-propagating Abbott waves ±vªe i(kr°!t) 0 rad ±v 0 ¥Uik±v w=k=°U 0 ª g r v 0 ª vv 0 v =g r v r  g~  v’ Abbott speed

July 30, 2001IAUC 1857 Line-Driven Instability u=v/v th for < L sob :  g/g ~  u Instability with growth rate  ~ g/v th ~ v/L sob ~100 v/R => e 100 growth!

July 30, 2001IAUC 1858 Growth and phase reversal of periodic base perturbation Radius (R * )

July 30, 2001IAUC 1859 Time snapshot of wind instability simulation Velocity Density CAK

July 30, 2001IAUC Wave transmission through sonic point r interior wind hydrostatic equilibrium r sonic a supersonic outflow velocity density

July 30, 2001IAUC Wave-leakage into outflowing wind Cranmer 1996, PhD.

Pulsation-Induced Wind Variations in BW Vul Steve Cranmer, Harvard-Smithsonian Stan Owocki, Bartol/U. of Del.

July 30, 2001IAUC BW Vul light curve

July 30, 2001IAUC Wind variations from base perturbations in density and brightness log(Density) Velocity Radius wind base perturbed by  ~ 50 radiative driving modulated by brightness variations Abbott-mode“kinks” velocity “plateaus” shock compression

July 30, 2001IAUC Radial velocity Model Observations

July 30, 2001IAUC Dynamic Spectra Si IIISi IV

July 30, 2001IAUC Observations vs. Model C IVModel line

July 30, 2001IAUC HD64760 Monitored during IUE “Mega” Campaign ¥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. Radiation hydrodynamics simulation of CIRs in a hot-star wind Rotational Modulation of Hot-Star Winds

July 30, 2001IAUC Phase Bowing

July 30, 2001IAUC HD (B0Ia) Si IV observation kinematic model with m=l=4 NRP

July 30, 2001IAUC Dynamical wind profile variation from m=4 Sinusoidal perturbation

July 30, 2001IAUC WR6 - Pulsational model m=4 dynamical model NIV in WR 6

The Rocket Science of Launching Stellar Disks Stan Owocki UD Bartol Research Institute

July 30, 2001IAUC The Puzzle of Be Disks And most Be stars are not in close binary systems. Be stars are too old to still have protostellar disk. How do Be stars do this?? They thus lack outside mass source to fall into disk. So disk matter must be launched from star.

July 30, 2001IAUC Key Puzzle Pieces Stellar Wind –Driven by line-scattering of star’s radiation –Rotation can lead to Wind Compressed Disk (WCD) –But still lacks angular momentum for orbit Stellar Pulsation –Many Be stars show Non-Radial Pulsation (NRP) with m < l = Magnetic Spin-Up –B dipole moment arm R a < few R * ~ R corotation Here examine combination of #’s 1, 2, & 3 Stellar Rotation –Be stars are generally rapid rotators –V rot ~ km/s < V orbit ~ 500 km/s

July 30, 2001IAUC Launching into Earth Orbit Requires speed of ~ 18,000 mi/h (5 mi/s). Earth’s rotation is ~ 1000 mi/h at equator. Cannon atop high mountain  V ~ 18,000 mi/h  V ~ 17,000 mi/h Cannon at equator Launching eastward from equator requires only ~ 17,000 km/h. 1-(1- 1/18) 2 ~ 2/18 => ~10% less Energy

July 30, 2001IAUC Launching into Be star orbit Requires speed of ~ 500 km/sec. Be star rotation is often > 250 km/sec at equator. Launching with rotation needs < 250 km/sec Requires < a quarter of the energy! Localized surface ejection self selects orbiting material. V rot = 250 km/sec  V=250 km/sec

July 30, 2001IAUC SPH simulations - P. Kroll gas ejection at 100 km/s “magnetic loop”

July 30, 2001IAUC Line-Profile Variations from Non-Radial Pulsation Wavelength (V rot =1) Flux Rotation + NRP NRP-distorted star (exaggerated) Line-Profile with:

July 30, 2001IAUC NRP Mode Beating l=3, m=2 l=2, m=1l=4, m=2

July 30, 2001IAUC NonRadial Radiative Driving Light has momentum. Pushes on gas that scatters it. Drives outflowing “stellar wind”. Pulsations distort surface and brightness. Could this drive local gas ejections into orbit??

July 30, 2001IAUC CIR from Symmetric Bright Spot on Rapidly Rotating Be Star V rot = 350 km/s V orbit = 500 km/s Spot Brightness= 10 Spot Size = 10 o

July 30, 2001IAUC Symmetric Spot with Stagnated Driving

July 30, 2001IAUC Symmetric Prominence/Filament

July 30, 2001IAUC Time Evolution of Single Prograde Spot

July 30, 2001IAUC Time Evolution of m=4 Prograde Spot Model

July 30, 2001IAUC Summary High-freq. p-modes feed line-driven instability g-modes can “leak” into wind Radial pulsational light curve modulates mass loss –distinctive Abbott kinks with velocity plateaus NRP light variations can lead to CIRs in Be stars NRP resonances might induce “orbital mass ejection”

July 30, 2001IAUC Inward propagation of Abbott wave v r gg