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The empirical upper limit for mass loss of cool main sequence stars
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Astronomy Astrophysics manuscript no. stepien c? ESO 2008
February 27, 2008
The empirical upper limit for mass loss of cool main sequence
stars
Anna Lednicka and K. Ste?pien?
Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
email: lednicka@astrouw.edu.pl, kst@astrouw.edu.pl
Received ...;accepted ...
ABSTRACT
Context. The knowledge of mass loss rates due to thermal winds in cool dwarfs is of crucial importance for modeling evolution of
physical parameters of main sequence single and binary stars. Very few, sometimes contradictory, measurements of such mass loss
rates exist up to now.
Aims. We present a new, independent method of measuring an amount of mass lost by a star during its past life.
Methods. It is based on the comparison of the present mass distribution of solar type stars in an open cluster with the calculated
distribution under an assumption that stars with masses lower than Mlim have lost an amount of mass equal to ?M. The actual value
of ?M or its upper limit is found from the best fit.
Results. Analysis of four clusters: Pleiades, NGC 6996, Hyades and Praesepe gave upper limits for ?M in three of them and the
inconclusive result for Pleiades. The most restrictive limit was obtained for Praesepe indicating that the average mass loss rate of cool
dwarfs in this cluster was lower than 6× 10?11 M⊙/yr. With more accurate mass determinations of the solar type members of selected
open clusters, including those of spectral type K, the method will provide more stringent limits for mass loss of cool dwarfs.
Key words. stars: activity – stars: late-type – stars: mass loss – stars: winds, outflows
1. Introduction
Chromospheric-coronal activity is ubiquitous in cool stars pos-
sessing subphotospheric convection zones. Hot coronas result in
existence of thermal winds carrying away stellar mass and an-
gular momentum. The precise knowledge of the mass loss rate
(M
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