Departures from LTE for neutral Li in late-type stars^*

¹ European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, 857 48 Garching bei München, Germany e-mail: klind@eso.org
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 857 41 Garching bei München, Germany
³ Department of Physics & Astronomy, Uppsala University, Box 515, 751 20 Uppsala, Sweden

Received: 28 March 2009
Accepted: 17 May 2009

Abstract

We perform non-LTE calculations of lithium in late-type stars for a wide range of stellar parameters, including quantum mechanical cross-sections for collisions with neutral hydrogen and the negative hydrogen ion. Non-LTE abundance corrections for the lithium resonance line at 670.7 nm and the subordinate line at 610.3 nm, are calculated using 1D MARCS model atmospheres spanning a grid T_eff = [4000, 8000] K, log g = [1.0, 5.0], and [Fe/H] = [0.0, -3.0], for lithium abundances in the range A(Li) = [-0.3, 4.2]. The competing effects of ultraviolet over-ionization and photon losses in the resonance line govern the behaviour of the non-LTE effects with stellar parameters and lithium abundance. The size and sign of the non-LTE abundance corrections vary significantly over the grid for the 670.7 nm line, but are typically positive and below 0.15 dex for the 610.3 nm, line. The new collisional data play a significant role in determining the abundance corrections.