Contribution à l'étude des spectres composites^*

VIII. HD 174016-7, une étoile Ap associée à une géante G Contribution to the study of composite spectra VIII. HD 174016-7, an Ap star with a giant G

¹ Observatoire Midi-Pyrénées, Laboratoire d'astrophysique (UMR 5572), 14 avenue Édouard Belin, F-31400 Toulouse, France
² The Observatories, Madingley Road, Cambridge CB3 0HA, UK
³ Observatoire de Genève, CH-1290 Sauverny, Suisse

Received: 23 July 1999
Accepted: 27 August 1999

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-Pyrénées. 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 m_v = 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.