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Structure and modelling of the stellar chromospheres and coronae

I. Busá has performed a detailed study on the diagnostic power of the CaII InfraRed Triplet (CaIIIRT: $\lambda=$ 8498, 8542, 8662 Å) profiles by means of NLTE calculations of the line profiles with treatment of UV line-blanketing, for a wide grid of photospheric models selected from the NextGen database (()). These calculations has been used to estimate the sensitivity of the profiles to changes in stellar parameters and the effect of departures from LTE. In particular this analysis has shown that, even the less active star show a filling in of the CaIIIRT cores indicating that, the CaIIIRT lines, could be useful diagnostic of the basal chromosphere. For example, using the Sun as ``template'' star leads to a systematic underestimation of the chromospheric emission in solar-type stars (see Fig. 1.5).

Figure 1.5: Solar profile of the $\lambda8498$ line (solid, thick line), compared to the synthetic photospheric profile of a star with \ensuremath{T_\mathrm{eff}}=5780 K and \ensuremath{\log g}=4.44 (dashed line). The residual profile (solid, thin line) is also shown (from ()).
\begin{figure}\centerline{\psfig{file=stars/Fig1-busa.ps,width=8cm,angle=90}}\end{figure}


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Next: Magnetic activity and dynamics Up: Magnetic activity and variability Previous: Magnetic activity and variability   Contents   Index
Innocenza Busa' 2005-11-14