Granulation signatures in the spectrum of the very metal-poor red giant HD 122563

摘要: A very high resolution (R = λ/Δλ 200, 000), signal-to-noise ratio (S/N 340) blue-green spectrum of the metal-poor ([Fe/H] –2.6) red giant star HD 122563 has been obtained by us at McDonald Observatory. We measure asymmetries and core wavelengths a set unblended Fe I lines covering wide range line strength. Line bisectors exhibit characteristic C-shape signature surface convection (granulation) they span from about 100 m s–1 in strongest features to 800 weakest ones. Core wavelength shifts –100 –900 s–1, depending on In general, larger blueshifts are observed weaker lines, but there is increasing scatter with residual flux. Assuming local thermodynamic equilibrium (LTE), we synthesize same spectral using state-of-the-art three-dimensional (3D) hydrodynamic simulation for stellar atmosphere fundamental parameters similar those 122563. find good agreement between model predictions observations. This allows infer an absolute zero point radial velocity. Moreover, it indicates that structure dynamics realistic, thus providing support previous claims large 3D-LTE corrections elemental abundances stars standard 1D-LTE spectroscopic analyses, as suggested used here.