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Astron. Astrophys. 327, 614-619


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Circumstellar dust shells around long-period variables

VI. An approximative formula for the mass loss rate of C-rich stars

T.U. Arndt, A.J. Fleischer, and E. Sedlmayr

Technische Universität Berlin, Institut für Astronomie und Astrophysik, PN 8-1, Hardenbergstr. 36, D-10623 Berlin, Germany

Received 23 December 1996 / Accepted 27 May 1997

Abstract

We present an equation which relates the six parameters of dynamical wind models to the resulting mass loss rate. These six parameters are the stellar temperature, the stellar luminosity, the stellar mass, the abundance ratio of carbon to oxygen, the pulsational period and the velocity amplitude of the pulsation. The equation is constructed by applying the maximum-likelihood method to a grid of 48 dynamical models. These models of circumstellar dust shells around carbon-rich long-period variables comprise the calculation of time-dependent hydrodynamics as well as a detailed treatment of dust formation, growth and evaporation.

The main influence on the mass loss rate is given by the stellar temperature, the stellar mass and luminosity. The influence of the carbon abundance, the pulsational period and the amplitude of the piston are almost negligible.

As this mass loss equation is based on physical models it is free of additional arbitrary parameters and could therefore serve as a more reliable description of the mass loss rate e.g. in stellar evolution calculations.

By applying the same method we also constructed two equations which relate the six parameters of dynamical wind models to the averaged outflow velocity and to the averaged dust-to-gas ratio respectively.

Key words: stars: carbon - stars: circumstellar matter - stars: late-type - stars: mass-loss - stars: variables (other)

Send offprint requests to: T.U. Arndt (Arndt@physik.TU-Berlin.DE)


© European Southern Observatory (ESO) 1997

Online publication: October 14, 1997
Last change: April 6, 1998
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