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 Winds found in all luminous stars: Kudritzski https://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):

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 Angstroms Fullerton et al. 2006, ApJ, 637, 1025

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:

IR and Radio Excess Emission f-f (Bremsstrahlung) emission from outer parts of wind; excess flux at long wavelengths kν ~ ν -2 higher 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)

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

Theory of Radiation-Driven Winds see handout from Kuditzki, Pauldrach & Puls 1988, O Stars and WR Stars, NASA SP-497 https://ntrs.nasa.gov/search.jsp?R=19890002286

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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)