Characteristics of the Fe II and C II emission in high-resolution IUE spectra (2300-3000 A) of Alpha Orionis

A study is presented of Fe II and C II emission features in the 2300-3000 A region of four high-resolution IUE spectra of Alpha Ori obtained during the period 1978 April-1982 November. A set of 42 unmutilated, unblended Fe II lines of multiplets UV 1-3, 32-33, 35-36, and 60-64 and the C II (UV 0.01) intercombination lines have been identified and measured to determine their velocities, fluxes, and asymmetries. A correlation of Fe II line asymmetry with intrinsic line strength indicates a velocity field which is initially constant, then algebraically increases with radius to a maximum value and then decreases significantly before reaching an asymptotic flow speed far from the star. The mean velocity of the chromospheric regions emitting Fe II does not appear to differ substantially from the time-average of the photospheric velocity, but there is evidence that the two regions are not strongly coupled and thus that the chromosphere does not strictly follow the semiperiodic 6 year pulsations of the photosphere. An analysis of the C II line fluxes produces estimates of the electron density in the chromosphere in the range 3.2 x 10 to the 7th-1.3 x 10 to the 8th per sq cm and indicates that the region emitting C II is geometrically thick, extending at least one-tenth, and perhaps as far as 1.2, photospheric radii from the base of the chromosphere.