Cool Stars 14 - Submitted Abstract # 30
This version created on 05 October 2006

A new method to measure Ca II H&K emission in very fast rotating stars


Christian Schroeder, Hamburger Sternwarte
Ansgar Reiners, Hamburger Sternwarte, Max-Planck-Institut fuer Sonnensystemforschung
Juergen H.M.M. Schmitt, Hamburger Sternwarte

Since Olin C.  Wilson began his research of stellar activity cycles in
1966, many projects have been carried out using the Mt.  Wilson
S-Index as a measure for chromospheric activity.  A known drawback of
this method is the fact that it can only be applied to slow rotating
stars, due to the fact that in fast rotators the emission features are
heavily broadened, leading to a loss of measurable flux outside the H
and K filters.  We have analysed solar-like stars ranging from Teff=
5200  to 7800  K with rotational velocities up to 200  km/s in our
sample of 328 FOCES and 99 FEROS spectra.  We present a newly
developed method to also measure Ca II H&K emission features in very
fast rotating stars by comparing the line shapes from known inactive
slow rotating template stars that have been artifically broadened to
those of fast rotating stars.  Our method has proven to produce
consistent results where S-Index values are available.

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