STATISTICAL EQUILIBRIUM OF LITHIUM IN THE ATMOSPHERES OF LATE-TYPE STARS - LITHIUM-RICH G-K GIANTS

The calculations of statistical equilibrium of lithium in the atmosphe res of G-K giants are discussed. The studies are carried out for a 20- level model of the Li atom by the complete-linearization method. Allow ance is made for the blanketing effect produced by atomic, ionic, and molecular absorption. The dependence of the parameters of Li absorptio n lines on the model-atmosphere parameterslog g and [Fe/H] is analyzed . It is shown that: (i) the non-LTE effects in Li lines differ markedl y for specific K giants; the abundance correction due to these effects varies over a wide range: from -0.4 dex (for HD 112127) to +0.2 dex ( for Capella B); (ii) for K giants with T-eff < 4500 K, the non-LTE equ ivalent widths of saturated absorption lines are less sensitive to log g and [Fe/H] than their LTE values; and (iii) the solutions of the no n-LTE problem for 6-level and 20-level model atoms are very close. For several giants, the Lithium abundance has been redetermined by taking into account the departures from LTE.