Semi-empirical models of the wind in cool supergiant starsA self-consistent semi-empirical model for the wind of the supergiant in zeta Aurigae type systems is proposed. The damping of the Alfven waves which are assumed to drive the wind is derived from the observed velocity profile. Solution of the ionization balance and energy equation gives the temperature structure for given stellar magnetic field and wave flux. Physically acceptable solutions of the temperature structure place limits on the stellar magnetic field. A crude formula for a critical mass loss rate is derived. For a mass loss rate below the critical value the wind cannot be cool. Comparison between the observed and the critical mass loss rate suggests that the proposed theory may provide an explanation for the coronal dividing line in the Hertzsprung-Russell diagram. The physical explanation may be that the atmosphere has a cool wind, unless it is physically impossible to have one. Stars which cannot have a cool wind release their nonthermal energy in an outer atmosphere at coronal temperatures. It is possible that in the absence of a substantial stellar wind the magnetic field has less incentive to extend radially outward, and coronal loop structures may become more dominant.
Document ID
19890007190
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Kuin, N. P. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ahmad, Imad A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
September 5, 2013
Publication Date
June 1, 1988
Publication Information
Publication: ESA, Proceedings of the Celebratory Symposium on a Decade of UV Astronomy with the IUE Satellite, Volume 2