Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 368, Issue 3, Pages 1145-1150Publisher
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2006.10190.x
Keywords
MHD; waves; stars : magnetic fields; stars : mass-loss
Categories
Ask authors/readers for more resources
Cool stars at giant and supergiant evolutionary phases present low-velocity and high-density winds, responsible for the observed high mass-loss rates. Although presenting high luminosities, radiation pressure on dust particles is not sufficient to explain the wind acceleration process. Among the possible solutions to this still unsolved problem, Alfven waves are, probably, the most interesting for their high efficiency in transfering energy and momentum to the wind. Typically, models of Alfven wave driven winds result in high-velocity winds if they are not highly damped. In this work, we determine self-consistently the magnetic field geometry and solve the momentum, energy and mass conservation equations, to demonstrate that even a low-damped Alfven wave flux is able to reproduce the low-velocity wind. We show that the magnetic flux tubes expand with a super-radial factor of S > 30 near the stellar surface, larger than that used in previous semi-empirical models. The rapid expansion results in a strong spatial dilution of the wave flux. We obtained the wind parameter profiles for a typical supergiant star of 16 M-circle dot. The wind is accelerated in a narrow region, coincident with the region of high divergence of the magnetic field lines, up to 100 km s(-1). For the temperature, we obtained a slight decrease near the surface for low-damped waves, because the wave heating mechanism is less effective than the radiative losses. The peak temperature occurs at r similar or equal to 1.5 r(0) reaching 6000 K. Propagating outwards, the wind cools down mainly due to adiabatic expansion.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available