Influence of chemi-ionization and chemi-recombination processes on hydrogen line shapes in M dwarfs

¹ Institute of Physics, PO Box 57, 11001 Belgrade, Serbia e-mail: mihajlov@phy.bg.ac.yu
² Isaac Newton Institute of Chile, Yugoslavia Branch
³ Astronomical Observatory, Volgina 7, 11160 Belgrade 74, Serbia
⁴ Depart. of Phys. and Astronomy and Center for Simulat. Physics, University of Georgia, Athens, GA 30602, USA
⁵ Hamburger Sternwarte, Universitaet Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁶ CRAL/ENS, 46 allée d'Italie, 69634 Lyon Cedex 07, France

Received: 21 March 2007
Accepted: 20 May 2007

Abstract

Aims.We study the influence of chemi-ionization in collisions and inverse chemi-recombination processes on the population of higher levels and consequently on profiles of hydrogen lines in the atmospheres of late type (M) stars.

Methods.Modeling, using general stellar atmosphere code PHOENIX to reveal the importance of the inclusion of such processes.

Results.We demonstrate for the first time observationally detectable effects of these chemi-processes on stellar spectra.

Conclusions.It is very important to include chemi-ionization and chemi-recombination processes in modeling of atmospheres of late type stars, especially if one wants to use line profiles for diagnostics of stellar photospheres and lower chromospheres.