An Analysis of the Cepheid Variable RT Aurigae

High dispersion spectra of the cepheid variable RT Aurigae have been used for an analysis of the parameters of the stellar atmosphere over a cycle of pulsation. Eighteen of these spectra were utilized for a study of the radial velocities. The displacement curve derived from the velocities was utilized with the light and colour curves of Eggen, Gascoigne & Burr to furnish by the application of Wesselink's method, a value of $$R/{R}_{\odot}\,=\,33\cdot 7$$ . A differential curve of growth analysis relative to the Sun has been carried out at eleven phases to evaluate the variation of the atmospheric parameters. The range in θ_exc is from 0·94 to 1·07. The variation of ρk is by a factor of ten over the cycle. A second hump in this curve at phase 0·68 P is perhaps a result of the sudden onset of a pulse of compression. Mean abundances relative to [Fe] have been derived for 21 elements. A general deficiency in s -process elements is seen in comparison with those formed by the e -process.