Contribution à l'étude des spectres composites

Abstract

HD 174016-7, listed by [Hynek (1938)] as a star having a composite spectrum, was on our observing programmes of such objects carried out both at the Cambridge Observatories and at the Observatoire Midi-Pyrenees. Most of the observations were made with the CORAVEL spectrovelocimeter of the Swiss telescope at the Observatoire de Haute-Provence. We find that this star is a long-period spectroscopic binary with two correlation dips; we obtain the following orbital elements: days; T = JD 2450605.2; ; ; km s-1 ; km s-1 ; km s-1 ; Gm; Gm; ; . The primary is a giant star of spectral type near G6III, and the hot dwarf secondary is found to be a peculiar A star of type A0p Sr, Cr, Eu, Si; so HD 174016-7 is, to our knowledge, the second discovered composite-spectrum binary with a Ap-type hot component. A confrontation with Hipparcos data suggests and mv = 0.6 mag. On the basis of very accurate masses of main sequence stars by [Andersen (1991),] we estimate the mass, , of the giant primary, the orbital inclination, , and the mean linear separation of the components, AU. The evolutionary status of the system is discussed using [Schaller et al. (1992)] diagram for stars of solar metallicity. Theoretical masses suggested by this diagram confirm the proposed model.