Astron. Astrophys. Suppl. Ser. 140, 279-285

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

N. Ginestet¹ - R.F. Griffin² - J.M. Carquillat¹ - S. Udry³

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

Reçu le 23 juillet ; accepté le 27 août 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: P = 3097.9 days; T = JD 2450605.2; $\omega = 204\hbox{$.\!\!^\circ$ }8$; e = 0.600; K₁ = 12.95 km s^-1; K₂ = 15.14 km s^-1; V₀ = -1.65 km s^-1; $a_1 \sin i = 441.1$ Gm; $a_2 \sin i = 516.0$ Gm; $M_1 \sin^3i = 1.967~M_\odot$; $M_2\sin^3i = 1.681~M_\odot$. 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 = 0and m_v = 0.6 mag. On the basis of very accurate masses of main sequence stars by Andersen (1991), we estimate the mass, $M_1 = 2.8~M_\odot$, of the giant primary, the orbital inclination, $i = 63^\circ$, and the mean linear separation of the components, a = 7.2 AU. The evolutionary status of the system is discussed using Schaller et al. (1992) $M_{\rm bol} / T_{\rm eff}$ diagram for stars of solar metallicity. Theoretical masses suggested by this diagram confirm the proposed model.

Key words: stars: individual: HD 174016-7 -- binaries: spectroscopic; symbiotic -- stars: fundamental parameters