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Disks formed by Rotation Induced Bi-stability

Published online by Cambridge University Press:  12 April 2016

Henny J.G.L.M. Lamers ,
Jorick S. Vink ,
Alex de Koter  and
Joseph P. Cassinelli
Henny J.G.L.M. Lamers
Affiliation:
Astronomical Institute, Utrecht University, Princetonplein 5, NL-3584 CC, Utrecht, The Netherlands SRON Laboratory for Space Research, Utrecht, The Netherlands
Jorick S. Vink
Affiliation:
Astronomical Institute, Utrecht University, Princetonplein 5, NL-3584 CC, Utrecht, The Netherlands
Alex de Koter
Affiliation:
Astronomical Institute, University of Amsterdam, Kruislaan 403, NL-1098 SJ, Amsterdam, The Netherlands
Joseph P. Cassinelli
Affiliation:
Dept of Astronomy, University of Wisconsin, 475 N Charterstreet, Madison, WI 53706-1582, Madison, USA

Abstract

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We discuss the evidence for the existence of bi-stable stellar winds of early type stars, both theoretically and observationally. The ratio between the terminal wind velocity and the escape velocity drops steeply from about 2.6 for stars with Teff > 21 000 K to about 1.3 at Teff < 21 000 K. This is the bi-stability jump, which is due to a change in the ionization of the wind and in the wind driving lines. The mass loss rate increases across the jump by about a factor 2 to 5 from the hotter to the cooler stars. The mass flux from rapidly rotating stars can also show the bi-stability jump at some lattitude between the pole and the equator, with a slow high density wind in the equatorial region and a faster low density wind from the poles. This might explain the disks of rapidly rotating B[e] stars, formed by the Rotation Induced Bi-stability mechanism. We discuss the RIB mechanism and its properties. We also describe some future improvements of the model.

Type
Section II Theory of Non-spherical Winds
Information
International Astronomical Union Colloquium , Volume 169: Variable and Non-spherical Stellar Winds in Luminous Hot Stars , 1999 , pp. 159 - 168
Copyright
Copyright © Springer-Verlag 1999

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