Curves of growth of neutral and ionized atoms in the spectrum of alpha Persei.

Abstract

Intensities of one thousand lines in the spectrum of a Persei have been determined recently from high dispersion spectra, 4 to 7 A7mm, using the Observatory intensitometer. Curves of growth, which relate the intensity of a line to the number of atoms which produce it, have been obtained for a number of atoms by plotting the stellar line intensities against solar f-values. It was found that the shape of the curves for neutral atoms is different from that for ionized atoms. The observations were fitted to theoretical curves given by Menzel and by Unso~ld, and the variable parameters of excitation temperature, damping factor and turbulent velocity were calculated for each atom. Values for a few atoms are given in the accompanying table. r - V No. of Atom km/sec Lioes Fe 1 49505K 1.3 X 106 5.0 325 Ti 1 5600 3.9 53 Cr 1 5350 1.6 4.6 29 Fe II 4500 0.2 7.5 60 Ti II 5350 0.1 6.1 62 Cr II 5400 - 8.3 25 When lines produced by neutral and ionized atoms of the same element are compared it appears that, for the neutral atom, I. the excitation temperature is somewhat higher; 2. the damping factor is greater, i.e., the pressure is greater; 3. the turbulent velocity is less. Though the observations and the method are such that these conclusions cannot be considered final, they suggest that there is appreciable stratification in the atmosphere of this supergiant star, with the mean position of the ionized atoms lying above that of the neutral atoms. Dominion Astrophysical Observatory, Victoria, B. C.