Granulation in K-type dwarf stars II. Hydrodynamic simulations and 3D spectrum synthesis

摘要: Aims. To explore the impact of surface inhomogeneities on stellar spectra, granulation models need to be computed. Ideally, most fundamental characteristics these should carefully tested before applying them study more practical matters, such as derivation photospheric abundances. Our goal is analyze particular case a K-dwarf. Methods. We construct three-dimensional radiative-hydrodynamic model atmosphere parameters $T_{\rm eff}=4820$ K, $\log g=4.5$, and solar chemical composition. Using this 3D spectrum synthesis, we computed number Fe i and Fe ii line profiles. The observations presented in first paper series were used test predictions. effects rotation instrumental imperfections are taken into account synthesis spectral lines. Results. theoretical line profiles show typical signatures granulation: lines asymmetric, with their bisectors having characteristic C-shape core wavelengths shifted respect laboratory values. span from about 10 250 m s -1 , depending strength, stronger features showing larger span. corresponding wavelength shifts range -200 m s  for weak Fe i lines almost +100 m s  in strong Fe i features. Based observational results for Sun, argue that there no shift $EW\gtrsim100$ mA. cores strongest contributions uncertain top layers model, where non-LTE presence chromosphere, which important real stars, not accounted for. Fe ii lines suffer due deeper formation depth makes experience temperature velocity contrasts. For example, weakest Fe ii lines -600 m s . comparison predictions observed Fe i line our reference star, HIP 86 400, shows excellent agreement, exception features, suspect inaccurate Since limitation does affect predicted equivalent widths significantly, consider 3D model validated abundance work.