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Stellar Winds of Massive Stars Lamers & Cassinelli (1999)

Stellar Winds of Massive Stars Lamers & Cassinelli (1999). P Cygni Lines Emission Lines IR and Radio Excess Emission Theory of Radiation Driven Winds. [Steven Cranmer, CfA]. Stellar Wind Outflows.

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Stellar Winds of Massive Stars Lamers & Cassinelli (1999)

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  1. Stellar Winds of Massive Stars Lamers & Cassinelli (1999) P Cygni Lines Emission Lines IR and Radio Excess Emission Theory of Radiation Driven Winds

  2. [Steven Cranmer, CfA]

  3. Stellar Wind Outflows • Winds found in all luminous stars: Kudritzskihttps://www.ifa.hawaii.edu/users/kud/windsfromhotstars/hotwinds.html • Mass loss by radiative winds: momentum of radiation field captured by opaque lines in UV • loss rates: 10-6 solar masses/yr (⅓ Earth/yr) • terminal velocities: 103 km/sec • velocity law (β≈0.8):

  4. P Cygni Lines • formed by scattering in resonance lines • examples in IUE Atlas of O-type Spectra • terminal velocity, β determined but hard to get mass loss rate: need ionization model and unsaturated lines • need detailed structure of filling factor • FUSE: P V 1118, 1128 AngstromsFullerton et al. 2006, ApJ, 637, 1025

  5. Emission Lines • Hα; Paschen, Brackett lines in near IR • He II 1640, 4686 • numerous N, C lines in WR stars • formed by recombination (density2) in the base level of wind • strength depends on temperature and:

  6. IR and Radio Excess Emission • f-f (Bremsstrahlung) emission from outer parts of wind; excess flux at long wavelengths • kν ~ ν -2higher opacity at longer wavelength • if know T(r), v(r) then can determine mass loss rate from excess • effective size larger at longer wavelength (τ=1)

  7. CHARA image of wind of P Cyg in H-band Richardson et al. 2013, ApJ, 769, 118

  8. Theory of Radiation-Driven Winds • see handout from Kuditzki, Pauldrach & Puls1988, O Stars and WR Stars, NASA SP-497https://ntrs.nasa.gov/search.jsp?R=19890002286

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  10. Velocity Density Radiation-Driven Winds from Hot-Stars • For hot, luminous stars the driving is generally thought to stem from radiation pressure acting through line scattering. • The Doppler shift of the line-profile within the expanding wind effectively “sweeps out” the star’s continuum momentum flux. • This makes the driving force a function of the wind velocity and acceleration, leading to strong instabilities that likely make such winds highly turbulent.

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

  12. To really know a star ... get a spectrum • “If a picture is worth a thousand words, then a spectrum is worth a thousand pictures.”(Prof. Ed Jenkins, Princeton University)

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