Coronal winds powered by radiative driving

Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
e-mail: l.lucy@imperial.ac.uk

Received: 28 December 2011
Accepted: 10 July 2012

Abstract

A two-component phenomenological model developed originally for ζ Puppis is revised in order to model the outflows of late-type O dwarfs that exhibit the weak-wind phenomenon. With the theory’s standard parameters for a generic weak-wind star, the ambient gas is heated to coronal temperatures  ≈3 × 10⁶ K at radii  ≳ 1.4 R, with cool radiation-driven gas being then confined to dense clumps with filling factor  ≈0.02. Radiative driving ceases at radius  ≈2.1   R when the clumps are finally destroyed by heat conduction from the coronal gas. Thereafter, the outflow is a pure coronal wind, which cools and decelerates reaching ∞ with terminal velocity  ≈1000 km s^-1.