Teff and logg dependence of velocity fields in M-stars

We present an investigation of velocity fields in early to late M-type hydrodynamic stellar atmosphere models. These velocities will be expressed in classical terms of microand macroturbulent velocities for usage in 1D spectral synthesis. The M-star model parameters range between logg of 3.0 – 5.0 and Teff of 2500 K – 4000 K. We characterize the Teffand logg-dependence of the hydrodynamical velocity fields in these models with a binning method, and for the determination of micro-turbulent velocities, the Curve of Growth method is used. The macro-turbulent velocities are obtained by convolutions with Gaussian profiles. Velocity fields in M-stars strongly depend on logg and Teff. Their velocity amplitudes increase with decreasing logg and increasing Teff. The 3D hydrodynamical and 1D macro-turbulent velocities range from ∼ 100 m/s for cool high gravity models to ∼ 800 m/s–1000 m/s for hot models or models with low logg. The micro-turbulent velocities range in the order of ∼ 100 m/s for cool models, to ∼ 600 m/s for hot or low logg models. Our M-star structure models are calculated with the 3D radiative-hydrodynamics (RHD) code CO5BOLD. The spectral synthesis on these models is performed with the line synthesis code LINFOR3D.