Stellar gravities from metallic line profiles, with application to Arcturus. The effective temperature of Arcturus

The damping wings of spectral line profiles of metals are sensitive to gas pressure and may be used to measure stellar gravity. It is suggested that the method is made insensitive to effective temperature by measuring the metal abundance from weak lines that have the same lower level as the strong damping line. The gravity of Arcturus is determined from the profile of the line 5269.5 Fe I, the damping constant having been determined from the profile of the corresponding solar line. The measured gravity is log g = 1.48 ± 0.15 corresponding to a mass of 0.61 ± 0.32 M⊙ for an angular diameter of 0.0201 arcsec. As part of the analysis, the determination of the effective temperature of Arcturus from the flux distribution in its spectrum is rediscussed and a revised value of 4400+60 K−30 K is proposed. A microturbulence of 2.2 ± 0.2 km/s is also proposed.