Effect of the microturbulence parameter on the Color-Magnitude Diagram

Author(s)
Josefina Montalban, Johannes Nendwich, Ulrike Heiter, Friedrich Kupka, Ernst Paunzen, Barry Smalley
Abstract

Microturbulence is usually treated in model atmospheres as a free parameter (ξt) that allows to re-establish agreement among abundances derived from different lines. Even if this parameter is a consequence of treating a 3D problem as a 1D one, it seems clear that microturbulence is linked to the velocity field within the atmosphere, and therefore to convection in the external layers. The values of the parameter as determined from observations show a dependence both on effective temperature and on surface gravity. In this paper we study how the microturbulence parameter used in the atmosphere models affects the theoretical color-magnitude diagram (CMD). First, in the Main Sequence (MS) domain due to the dependence of the microturbulence parameter on Teff; and second, in the giant branch (Pre-main sequence and Red Giant Branch) where several photometric indexes show a large variation due to the increase of the microturbulence parameter as the stellar gravity decreases. We predict then a significant change in the CMD, as well as in the color-temperature calibrations, if variations of ξt such as those observationally determined are included in theoretical CMD computations.

Organisation(s)
Department of Astrophysics
External organisation(s)
Université de Liège, Uppsala University, Max-Planck-Institut für Astrophysik, Keele University
Pages
166-168
No. of pages
3
DOI
https://doi.org/10.1017/S1743921307000361
Publication date
2007
Austrian Fields of Science 2012
1030 Physics, Astronomy
Portal url
https://ucrisportal.univie.ac.at/en/publications/526052b6-2fe5-4faa-adba-747cb55faac1