Iron abundance in the atmosphere of Arcturus

Abstract: Abundance of iron in the atmosphere of Arcturus has been determined from the profiles or regions of the profiles of the weak lines sensitive to iron abundance. The selected lines of Fe I and Fe II were synthesized with the MARCS theoretical models of the atmosphere. From the observed profiles of lines available with a high spectral resolution in the atlas by Hinkle and Wallace (2005), the values of the iron abundance $A = 6.95 \pm 0.03$ and the radial-tangential macroturbulent velocity $5.6 \pm 0.2$ km/s were obtained for Arcturus. The same physical quantities were found for the Sun as a star; they are $7.42 \pm 0.02$ and $3.4 \pm 0.3$ km/s, respectively. For Arcturus, the iron abundance relative to the solar one was determined with the differential method as [Fe/H] $=-0.48 \pm 0.02$.