Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003csss...12.1134b&link_type=abstract
The Future of Cool-Star Astrophysics: 12th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (2001 July 30 - August
Astronomy and Astrophysics
Astrophysics
Radiative Transfer
Scientific paper
NLTE calculations of the profiles of the Ca II InfraRed Triplet (IRT: λ= 8498, 8542, 8662 Å) are performed for a grid of photospheric models with Teff=4200, 5200, 6200 K, log g=4.0, 4.5, 5.0 and metal=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 rhk found, for instance, by Chmielewski (2000) is mainly due to the effect of v sin i (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, \caindex, given by the difference between the calculated photospheric central intensity and the observed one. The correlation we find between this purely chromospheric index and rhk, for which we give two interpolation expressions, is more directly related to chromospheric activity.
Andretta Vincenzo
Busà I.
Gomez M. T.
Terranegra L.
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