EDP Sciences
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Volume 374, Number 1, July IV 2001
Page(s) 204 - 212
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010609

A&A 374, 204-212 (2001)
DOI: 10.1051/0004-6361:20010609

Eclipsing binaries with candidate CP stars

II. Parameters of the system V392 Carinae
Y. Debernardi and P. North

Institut d'Astronomie de l'Université de Lausanne, 1290 Chavannes-des-Bois, Switzerland

(Received 12 April 2001 / Accepted 26 April 2001 )

We present a detailed study of an eclipsing binary which had been classified Ap SrCrEu (Hartoog 1976) before being known as a binary. Radial velocities measured at the times of both quadratures allow us to obtain precise masses for both components, while the light curve yields the radii. The following ephemeris and fundamental parameters of the system were obtained: ${\rm HJD} = (2447999.7656\pm 0.0041) + (3.174990 \pm 0.000001) E$, e = 0.00, $i = 81.9\pm 0.1$°, $M_1 = 1.90 \pm 0.02 M_{\odot}$, $M_2 = 1.85 \pm 0.02 M_{\odot}$, $R_1 = 1.63\pm 0.03 R_{\odot}$, $R_2 = 1.60\pm 0.03 R_{\odot}$, $v\sin i_1 = 27.6\pm 3.5$ km s-1, $v\sin i_2 = 23.6\pm 3.6$ km s-1. The projected rotational velocities were determined by fitting a synthetic spectrum convolved with a rotational profile to the observed spectrum. A comparison of the spectra of V392 Car and of the normal A star Cox 98 , which has the same colour indices, shows that Sr is not overabundant and the metallicity of V392 Car is the same as that of the other cluster members. Therefore, V392 Car is a normal A2 star rather than an Ap star. The position of V392 Car in the HR diagram is entirely consistent with membership of the cluster NGC 2516. An independent estimate of the distance to this cluster was done using the parameters of the eclipsing system, and found to be in agreement with the Hipparcos one. A comparison of the parameters obtained from observations with predictions of internal structure models leads to a metallicity estimate ${\rm [M/H]}=0\pm 0.10$ dex for NGC 2516. This estimate is completely independent of any spectroscopic or photometric method (except for the $T_{\rm eff}$ determination) but relies on stellar structure models.

Key words: stars: peculiar -- stars: eclipsing binaries -- stars: spectroscopic binaries

Offprint request: Y. Debernardi, Yves.Debernardi@obs.unige.ch

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