1999A&AS..140..279G

HD 174016-7, listed by Hynek (1938CoPer...1...10H) 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: P=3097.9days; T=JD2450605.2; ω=204.8°; e=0.600; K₁=12.95km/s; K₂=15.14km/s; V₀=-1.65km/s; a₁sini=441.1Gm; a₂sini=516.0Gm; M₁sin³i=1.967M_☉; M₂sin³i=1.681M_☉. 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 M_v1=0 and m_v=0.6mag. On the basis of very accurate masses of main sequence stars by Andersen (1991) we estimate the mass, M₁=2.8M_☉, of the giant primary, the orbital inclination, i=63°, and the mean linear separation of the components, a=7.2AU. The evolutionary status of the system is discussed using Schaller et al. (1992) M_bol/T_eff diagram for stars of solar metallicity. Theoretical masses suggested by this diagram confirm the proposed model.