An analysis of the spectral line broadening of Arcturus

Abstract

Line broadening in 36 spectral lines of Arcturus is analyzed to obtain information on rotation and turbulence parameters. Spectral regions of approximately 18 A width with central wavelengths between 6010 and 6250 A were observed and analyzed in terms of a model of rotation, macroturbulence and microturbulence as the nonthermal sources of the broadening. The weak and strong lines are found to be compatible with a rotation rate of 2.4 + or - 0.4 km/sec and a radial-tangential macroturbulence dispersion of 5.1 + or - 0.2 km/sec, while the intermediate-intensity lines exhibit unexplained discrepancies. The microturbulence dispersion is found to vary with line strength, increasing from zero for the weak lines to 1.75 km/sec for the strong lines, and implying depth dependence.