POSTER PAPER 11.10
A Non-LTE Analysis of the Ca II Infrared Triplet as a Diagnostic Tool in Solar-type Stars
I. Busa', V. Andretta, M.T. Gomez, L. Terranegra
Institute: Hamburger Sternwarte
Institute: Osservatorio Astronomico di Capodimonte
Contact Email: ebu@na.astro.it
Abstract:
NLTE calculations of the profiles of the Ca II InfraRed Triplet (IRT:
lambda= 8498, 8542, 8662 A) are performed for a grid of photospheric
models with Teff=4200, 5200, 6200 K, logg=4.0, 4.5, 5.0 and [A/H]=0.0, -1.0,
-2.0, showing the sensitivity of the profiles to changes in stellar parameters
and the effect of departures from LTE.
Our analysis shows that the correlation between the observed
line central depression
and log R'HK found, for instance, by Chmielewski (2000) is mainly due
to the effect of vsini (via the rotation--activity correlation)
instead of being the result of a pure chromospheric filling-in of the line
core.
We therefore define a new activity index, RIRT , given by the difference
between the calculated photospheric central intensity and the observed one.
The correlation we find between this purely chromospheric index and logR'HK , for
which we give two interpolation expressions, is more directly related to
chromospheric activity.
Index Keywords: Radiative Transfer
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Manuscript submitted: 2001-Dec-28
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.