An O star has luminosity and drives a wind with terminal velocity .

PHYSICS · Multi-part · Fermi University Physics · Astrophysics & Cosmology · Stellar structure, energy generation and evolution · Stellar structure, energy generation and evolution

Stars from the Inside, Ch Stellar evolution: from the Hayashi track to the iron core, and the ages of clusters

Problem

An O star has luminosity

L = 10^{5}\,L_\odot

and drives a wind with terminal velocity

v_\infty = 2000\,\mathrm{km\,s^{-1}}

. ((a)) Estimate the single-scattering momentum limit on its mass-loss rate,

\dot M v_\infty \lesssim L/c

. ((b)) The star's wind is observed to have

\dot M = 3\times10^{-6}\,M_\odot\,\mathrm{yr}^{-1}

. Find the ratio of the observed rate to the single-scattering limit, and state what this ratio implies about how momentum is transferred to the wind.

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